Python subpackage import from neighboring subpackage

Consider the following file structure hierarchy:

MusicEditor (package)
        Converters (subpackage)
            ...
        Transformations (subpackage)
            ...
        Utility (subpackage)
            ...

What is the proper way to import a file/module from the utility subpackage into a file in the converters subpackage? e.g. import Utility/string.py into the file Converters/wav.py

How would I go about doing this?

---

EDIT in response to Ismael Infante

Would the following be correct?

Suppose that MusicEditor resided in /usr/something/MusicEditor. Then I would edit python path as follows?

PYTHONPATH = PYTHONPATH + /usr/something/

I would then add the init files to each directory as follows:

MusicEditor (package)
        __init__.py
        Converters (subpackage)
            __init__.py
            ...
        Transformations (subpackage)
            __init__.py
            ...
        Utility (subpackage)
            __init__.py
            ...

And then to include something from utilities into a file located in converters, I would simply go:

(MusicEditor/Converters/wav.py)

import MusicEditor.Utility.string

Is this correct? But I could also use the following relative path, right?

(MusicEditor/Converters/wav.py)

import ..Utility.string