Use python files as source for the UDF

[tkilias]

Background

• currently, we use wrapper functions with imports, classes and functions as source for the source code for the UDF
• another useful source might be python files, because then you can write your UDF as a normal python file
  • the only limitation is, you can't import it, if you use the global exa object. In this case, you need to use the mock which injects it.

Hints:

• Check if we can somehow reference the python file, maybe via importlib_resources and if we get a resource we load the source code from there
• Alternatively, check the type of the input and if it is str, use this string as source code
• Third, option might be pathlib Paths

Acceptance Criteria

• Users can use a python file as input of the udf mock