Merge smttask/tests/test_typing::test_pure_functions and with scityping/tests/test_purefunction
-> Should test specifying the type: PureFunction[[Any], int]

smttask_ml/tests/test_serialization to scityping/tests/test_scipy


In base.py: Remove the imports `from .functions import …`
- Logically functions.py comes after base.py
  Because of this, these imports are inside functions instead of at the top of the module
- Option: move `serialize_function` and `deserialize_function` to utils.py