Add get_parents function to ElementService

[MariusWirtz]

Fixes #697

[MariusWirtz]

@elcinsayin
please upgrade to this branch and test the get_parents function:

pip uninstall tm1py
pip install https://github.com/cubewise-code/tm1py/archive/refs/heads/feature/get-parents.zip

Let me know how it goes

[elcinsayin]

Thank you so much, will try it next week.

[elcinsayin]

I tried it. It retrieves all the parents when it's under different consolidated elements and it retrieves the immediate parent when it's under a consolidated element which is also under another consolidated element. Thank you so much.