docs: def get_file(self, user, handle):
          """Retrieve a file for a user.
  
          :returns: a :class:`pathlib.Path` instance to this file,
              or None if no file can be found for this handle.
          """
          user_dir = self.user_dir(user)
          if not user_dir.exists():
              return None
  
          if not is_valid_handle(handle):
              return None
  
          file_path = user_dir / handle
  
          if not file_path.exists() and not file_path.is_file():
              return None
  
          return file_path