Kivymd APK App (created with Buildozer) closes after opening up

I have created an APK file from Python Kivy & KivyMD, using Buildozer. When I open the app after installing it, it shows the splash image and then closes.
I have checked and found that their seems no issue in the main.py, as I have correctly listed Kivy & KivyMD in the requirements in the Buildozer.spec file. (kivy==2.0.0,kivymd==0.104.1)

This is my code..

main.py

import kivymd
from kivymd.app import MDApp
from kivymd.uix.screen import Screen
from kivy.lang import Builder
from kivymd.uix.button import MDRectangleFlatButton, MDFlatButton
from kivymd.uix.dialog import MDDialog
import helper
import model

class DemoApp(MDApp):
    def build(self):
        self.theme_cls.primary_palette = "Green"
        self.screen = Builder.load_string(helper.navigation_helper)
        return self.screen

    def show_data(self): #(self,obj):
        self.abc = model.chat(self.screen.ids.user_name.text)
        close_button = MDFlatButton(text='Close', on_release=self.close_dialog)
        self.dialog = MDDialog(title='First-aid Suggested..', text=self.abc, size_hint=(0.7, 1), buttons=[close_button])
        self.dialog.open()
    
    def close_dialog(self, obj):
        self.dialog.dismiss()

DemoApp().run()

model.py

import nltk
# nltk.download('punkt')
from nltk.stem.lancaster import LancasterStemmer
stemmer = LancasterStemmer()
import numpy
import random
import json
from keras.layers import *
from keras.models import *

with open("intents.json") as file:
    data = json.load(file)

words = []
labels = []
docs_x = []
docs_y = []

for intent in data["intents"]:
    for pattern in intent["patterns"]:
        wrds = nltk.word_tokenize(pattern)           # ['What', 'to', 'do', 'if', 'Cuts', '?']
        words.extend(wrds)
        docs_x.append(wrds)                          # input data (x)
        docs_y.append(intent["tag"])                 # corresponding output data (y)

    if intent["tag"] not in labels:
        labels.append(intent["tag"])                 # all possible output data

words = [stemmer.stem(w.lower()) for w in words if w != "?"]
words = sorted(list(set(words)))

labels = sorted(labels)


training = []
output = []

out_empty = [0 for _ in range(len(labels))]              # [1,2,3] [0,0,0]

for x, doc in enumerate(docs_x):
    bag = []

    wrds = [stemmer.stem(w) for w in doc]               # doc = ['What', 'to', 'do', 'if', 'Cuts', '?']   &    wrds = ['What', 'to', 'do', 'if', 'Cut', '?']

    for w in words:
        if w in wrds:
            bag.append(1)
        else:
            bag.append(0)
    output_row = out_empty[:]
    output_row[labels.index(docs_y[x])] = 1

    training.append(bag)
    output.append(output_row)

from keras.models import load_model
model = load_model("First_Aid_model.h5")

def bag_of_words(s,words):
  bag = [0 for _ in range(len(words))]
  s_words = nltk.word_tokenize(s)
  s_words = [stemmer.stem(word.lower()) for word in s_words]
  for se in s_words:
    for i, w in enumerate(words):
      if w == se:
        bag[i] = 1
  return bag


def chat(inp):
    results = model.predict([bag_of_words(inp,words)])
    result = results[0]
    results_index = numpy.argmax(result)
    tag = labels[results_index]
    if result[results_index] > 0.5:
      for tg in data["intents"]:
        if tg['tag'] == tag:
          responses = tg['responses']
      res = random.choice(responses).split('. ')
      res = [res[_]+'.' for _ in range(len(res)) if  not res[_].endswith('.')]
      res = ('n').join(res)
      return(res + "n")
    else:
      return("I didnt get that, try again")

helper.py

navigation_helper = """
Screen:
    MDNavigationLayout:
        ScreenManager:
            Screen:
                BoxLayout:
                    orientation: 'vertical'
                    MDToolbar:
                        title: "Navigation Drawer"
                        elevation: 10
                        left_action_items: [['menu', lambda x: nav_drawer.set_state('toggle')]]
                    Widget:
                    MDTextField:
                        id: user_name
                        hint_text: "Enter username"
                        helper_text: "or click on forgot username"
                        helper_text_mode: "on_focus"
                        icon_right: "redhat"
                        icon_right_color: app.theme_cls.primary_color
                        pos_hint:{'center_x': 0.5, 'center_y': 0.5}
                        size_hint_x:None
                        width:300
                        
                    MDRectangleFlatButton:
                        text: "Show"
                        pos_hint: {'center_x': 0.5, 'center_y': 0.5}
                        on_release: app.show_data()
                    
                    Widget:
                    
                    
                    
        MDNavigationDrawer:
            id: nav_drawer
            
            BoxLayout:
                orientation: 'vertical'
                padding: "8dp"
                spacing: "8dp"
                Image:
                    id: avatar
                    size_hint: (1,1)
                    source: "Capture.PNG"
                MDLabel:
                    text: "First-aid Bot"
                    font_style: "Subtitle1"
                    size_hint_y: None
                    height: self.texture_size[1]
                MDLabel:
                    text: "[email protected]"
                    size_hint_y: None
                    font_style: "Caption"
                    height: self.texture_size[1]
                ScrollView:
                        
                    MDList:
                        OneLineIconListItem:
                            text: "Profile"
                            IconLeftWidget:
                                icon: "face-profile"
                                    
                        OneLineIconListItem:
                            text: "Upload"
                            IconLeftWidget:
                                icon: "upload"
                                    
                        OneLineIconListItem:
                            text: "Logout"
                            IconLeftWidget:
                                icon: "logout"
                            
"""

buildozer.spec

[app]

# (str) Title of your application
title = Bot

# (str) Package name
package.name = bot

# (str) Package domain (needed for android/ios packaging)
package.domain = org.bot

# (str) Source code where the main.py live
source.dir = .

# (list) Source files to include (let empty to include all the files)
source.include_exts = py,png,jpg,kv,atlas

# (list) List of inclusions using pattern matching
#source.include_patterns = assets/*,images/*.png

# (list) Source files to exclude (let empty to not exclude anything)
#source.exclude_exts = spec

# (list) List of directory to exclude (let empty to not exclude anything)
#source.exclude_dirs = tests, bin

# (list) List of exclusions using pattern matching
#source.exclude_patterns = license,images/*/*.jpg

# (str) Application versioning (method 1)
version = 0.1

# (str) Application versioning (method 2)
# version.regex = __version__ = ['"](.*)['"]
# version.filename = %(source.dir)s/main.py

# (list) Application requirements
# comma separated e.g. requirements = sqlite3,kivy
requirements = python3,kivy==2.0.0,kivymd==0.104.1

# (str) Custom source folders for requirements
# Sets custom source for any requirements with recipes
# requirements.source.kivy = ../../kivy

# (list) Garden requirements
#garden_requirements =

# (str) Presplash of the application
#presplash.filename = %(source.dir)s/data/presplash.png

# (str) Icon of the application
#icon.filename = %(source.dir)s/data/icon.png

# (str) Supported orientation (one of landscape, sensorLandscape, portrait or all)
orientation = portrait

# (list) List of service to declare
#services = NAME:ENTRYPOINT_TO_PY,NAME2:ENTRYPOINT2_TO_PY

#
# OSX Specific
#

#
# author = © Copyright Info

# change the major version of python used by the app
osx.python_version = 3

# Kivy version to use
osx.kivy_version = 1.9.1

#
# Android specific
#

# (bool) Indicate if the application should be fullscreen or not
fullscreen = 0

# (string) Presplash background color (for new android toolchain)
# Supported formats are: #RRGGBB #AARRGGBB or one of the following names:
# red, blue, green, black, white, gray, cyan, magenta, yellow, lightgray,
# darkgray, grey, lightgrey, darkgrey, aqua, fuchsia, lime, maroon, navy,
# olive, purple, silver, teal.
#android.presplash_color = #FFFFFF

# (list) Permissions
#android.permissions = INTERNET

# (int) Target Android API, should be as high as possible.
#android.api = 27

# (int) Minimum API your APK will support.
#android.minapi = 21

# (int) Android SDK version to use
#android.sdk = 20

# (str) Android NDK version to use
#android.ndk = 19b

# (int) Android NDK API to use. This is the minimum API your app will support, it should usually match android.minapi.
#android.ndk_api = 21

# (bool) Use --private data storage (True) or --dir public storage (False)
#android.private_storage = True

# (str) Android NDK directory (if empty, it will be automatically downloaded.)
#android.ndk_path =

# (str) Android SDK directory (if empty, it will be automatically downloaded.)
#android.sdk_path =

# (str) ANT directory (if empty, it will be automatically downloaded.)
#android.ant_path =

# (bool) If True, then skip trying to update the Android sdk
# This can be useful to avoid excess Internet downloads or save time
# when an update is due and you just want to test/build your package
# android.skip_update = False

# (bool) If True, then automatically accept SDK license
# agreements. This is intended for automation only. If set to False,
# the default, you will be shown the license when first running
# buildozer.
# android.accept_sdk_license = False

# (str) Android entry point, default is ok for Kivy-based app
#android.entrypoint = org.renpy.android.PythonActivity

# (str) Android app theme, default is ok for Kivy-based app
# android.apptheme = "@android:style/Theme.NoTitleBar"

# (list) Pattern to whitelist for the whole project
#android.whitelist =

# (str) Path to a custom whitelist file
#android.whitelist_src =

# (str) Path to a custom blacklist file
#android.blacklist_src =

# (list) List of Java .jar files to add to the libs so that pyjnius can access
# their classes. Don't add jars that you do not need, since extra jars can slow
# down the build process. Allows wildcards matching, for example:
# OUYA-ODK/libs/*.jar
#android.add_jars = foo.jar,bar.jar,path/to/more/*.jar

# (list) List of Java files to add to the android project (can be java or a
# directory containing the files)
#android.add_src =

# (list) Android AAR archives to add (currently works only with sdl2_gradle
# bootstrap)
#android.add_aars =

# (list) Gradle dependencies to add (currently works only with sdl2_gradle
# bootstrap)
#android.gradle_dependencies =

# (list) add java compile options
# this can for example be necessary when importing certain java libraries using the 'android.gradle_dependencies' option
# see https://developer.android.com/studio/write/java8-support for further information
# android.add_compile_options = "sourceCompatibility = 1.8", "targetCompatibility = 1.8"

# (list) Gradle repositories to add {can be necessary for some android.gradle_dependencies}
# please enclose in double quotes 
# e.g. android.gradle_repositories = "maven { url 'https://kotlin.bintray.com/ktor' }"
#android.add_gradle_repositories =

# (list) packaging options to add 
# see https://google.github.io/android-gradle-dsl/current/com.android.build.gradle.internal.dsl.PackagingOptions.html
# can be necessary to solve conflicts in gradle_dependencies
# please enclose in double quotes 
# e.g. android.add_packaging_options = "exclude 'META-INF/common.kotlin_module'", "exclude 'META-INF/*.kotlin_module'"
#android.add_gradle_repositories =

# (list) Java classes to add as activities to the manifest.
#android.add_activities = com.example.ExampleActivity

# (str) OUYA Console category. Should be one of GAME or APP
# If you leave this blank, OUYA support will not be enabled
#android.ouya.category = GAME

# (str) Filename of OUYA Console icon. It must be a 732x412 png image.
#android.ouya.icon.filename = %(source.dir)s/data/ouya_icon.png

# (str) XML file to include as an intent filters in <activity> tag
#android.manifest.intent_filters =

# (str) launchMode to set for the main activity
#android.manifest.launch_mode = standard

# (list) Android additional libraries to copy into libs/armeabi
#android.add_libs_armeabi = libs/android/*.so
#android.add_libs_armeabi_v7a = libs/android-v7/*.so
#android.add_libs_arm64_v8a = libs/android-v8/*.so
#android.add_libs_x86 = libs/android-x86/*.so
#android.add_libs_mips = libs/android-mips/*.so

# (bool) Indicate whether the screen should stay on
# Don't forget to add the WAKE_LOCK permission if you set this to True
#android.wakelock = False

# (list) Android application meta-data to set (key=value format)
#android.meta_data =

# (list) Android library project to add (will be added in the
# project.properties automatically.)
#android.library_references =

# (list) Android shared libraries which will be added to AndroidManifest.xml using <uses-library> tag
#android.uses_library =

# (str) Android logcat filters to use
#android.logcat_filters = *:S python:D

# (bool) Copy library instead of making a libpymodules.so
#android.copy_libs = 1

# (str) The Android arch to build for, choices: armeabi-v7a, arm64-v8a, x86, x86_64
android.arch = armeabi-v7a

# (int) overrides automatic versionCode computation (used in build.gradle)
# this is not the same as app version and should only be edited if you know what you're doing
# android.numeric_version = 1

#
# Python for android (p4a) specific
#

# (str) python-for-android fork to use, defaults to upstream (kivy)
#p4a.fork = kivy

# (str) python-for-android branch to use, defaults to master
#p4a.branch = master

# (str) python-for-android git clone directory (if empty, it will be automatically cloned from github)
#p4a.source_dir =

# (str) The directory in which python-for-android should look for your own build recipes (if any)
#p4a.local_recipes =

# (str) Filename to the hook for p4a
#p4a.hook =

# (str) Bootstrap to use for android builds
# p4a.bootstrap = sdl2

# (int) port number to specify an explicit --port= p4a argument (eg for bootstrap flask)
#p4a.port =


#
# iOS specific
#

# (str) Path to a custom kivy-ios folder
#ios.kivy_ios_dir = ../kivy-ios
# Alternately, specify the URL and branch of a git checkout:
ios.kivy_ios_url = https://github.com/kivy/kivy-ios
ios.kivy_ios_branch = master

# Another platform dependency: ios-deploy
# Uncomment to use a custom checkout
#ios.ios_deploy_dir = ../ios_deploy
# Or specify URL and branch
ios.ios_deploy_url = https://github.com/phonegap/ios-deploy
ios.ios_deploy_branch = 1.7.0

# (str) Name of the certificate to use for signing the debug version
# Get a list of available identities: buildozer ios list_identities
#ios.codesign.debug = "iPhone Developer: <lastname> <firstname> (<hexstring>)"

# (str) Name of the certificate to use for signing the release version
#ios.codesign.release = %(ios.codesign.debug)s


[buildozer]

# (int) Log level (0 = error only, 1 = info, 2 = debug (with command output))
log_level = 2

# (int) Display warning if buildozer is run as root (0 = False, 1 = True)
warn_on_root = 1

# (str) Path to build artifact storage, absolute or relative to spec file
# build_dir = ./.buildozer

# (str) Path to build output (i.e. .apk, .ipa) storage
# bin_dir = ./bin

#    -----------------------------------------------------------------------------
#    List as sections
#
#    You can define all the "list" as [section:key].
#    Each line will be considered as a option to the list.
#    Let's take [app] / source.exclude_patterns.
#    Instead of doing:
#
#[app]
#source.exclude_patterns = license,data/audio/*.wav,data/images/original/*
#
#    This can be translated into:
#
#[app:source.exclude_patterns]
#license
#data/audio/*.wav
#data/images/original/*
#


#    -----------------------------------------------------------------------------
#    Profiles
#
#    You can extend section / key with a profile
#    For example, you want to deploy a demo version of your application without
#    HD content. You could first change the title to add "(demo)" in the name
#    and extend the excluded directories to remove the HD content.
#
#[app@demo]
#title = My Application (demo)
#
#[app:source.exclude_patterns@demo]
#images/hd/*
#
#    Then, invoke the command line with the "demo" profile:
#
#buildozer --profile demo android debug

According to me, the issue is coming as in the model.py file, I have imported modules like Keras, NLTK etc..and I am not mentioning them in requirements.
If this is the issue, then please give the complete statement which I should write in the requirements, according to my model.py & others
Please guide me.