Reformat swc.py docstrings, typing, and tests

[bvarjavand]

Reformat the code and tests to be similar to upload.py and session.py. This means:

• [ ] typing hints on every method and class
• [ ] google-formatted docstrings on every method and class
• [ ] input checking (TypeError and ValueError) on every input for every method
• [ ] tests on each method validating inputs
• [ ] tests on each method validating returns
• [ ] docstring on each test describing what it does

An example method which has been refomatted. An example method which has not been reformatted. Note the lack of type hints and type checking. An example which lacks documentation.