code: def _get_default_directory():
      
      return os.environ.get('PRE_COMMIT_HOME') or os.path.join(
          os.environ.get('XDG_CACHE_HOME') or os.path.expanduser('~/.cache'),
          'pre-commit',
      )
docs: Returns the default directory for the Store.  This is intentionally
      underscored to indicate that `Store.get_default_directory` is the intended
      way to get this information.  This is also done so
      `Store.get_default_directory` can be mocked in tests and
      `_get_default_directory` can be tested.