fix mypy errors about ipromise HOT 5 CLOSED

$ python -m poetry run mypy ipromise/
Success: no issues found in 6 source files

$ python -m poetry run mypy test/
test/test_overrides.py:4: error: Skipping analyzing "pytest": module is installed, but missing library stubs or py.typed marker  [import]
test/test_overrides.py:26: error: Function is missing a return type annotation  [no-untyped-def]
test/test_overrides.py:26: note: Use "-> None" if function does not return a value
test/test_overrides.py:162: error: Cannot instantiate abstract class "AbstractBaseClassHasAbstractMethod" with abstract attribute "f"  [abstract]
test/test_overrides.py:171: error: Function is missing a return type annotation  [no-untyped-def]
test/test_overrides.py:171: note: Use "-> None" if function does not return a value
test/test_overrides.py:181: error: Function is missing a return type annotation  [no-untyped-def]
test/test_overrides.py:181: note: Use "-> None" if function does not return a value
test/test_overrides.py:190: error: Function is missing a return type annotation  [no-untyped-def]
test/test_overrides.py:190: note: Use "-> None" if function does not return a value
test/test_implements.py:4: error: Skipping analyzing "pytest": module is installed, but missing library stubs or py.typed marker  [import]
test/test_implements.py:22: error: Function is missing a return type annotation  [no-untyped-def]
test/test_implements.py:22: note: Use "-> None" if function does not return a value
test/test_augments.py:4: error: Skipping analyzing "pytest": module is installed, but missing library stubs or py.typed marker  [import]
test/test_abc.py:4: error: Skipping analyzing "pytest": module is installed, but missing library stubs or py.typed marker  [import]
test/test_abc.py:4: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
Found 10 errors in 4 files (checked 6 source files)

$ python -m poetry update
Updating dependencies
Resolving dependencies... (38.4s)

  ValueError

  invalid literal for int() with base 10: b''

  at .venv-3.8.13_ubuntu-22.04_B/lib/python3.8/site-packages/cachy/stores/file_store.py:65 in _get_payload
       61│
       62│         with open(path, 'rb') as fh:
       63│             contents = fh.read()
       64│
    →  65│         expire = int(contents[:10])
       66│
       67│         # If the current time is greater than expiration timestamps we will delete
       68│         # the file and return null. This helps clean up the old files and keeps
       69│         # this directory much cleaner for us as old files aren't hanging out.