code: def drop_user(self, username: str) -> None:
      self._mts._match_call(("drop_user", username))
  
imports: import contextlib
  import os
  from typing import Any, Iterator, List, Optional, cast
  import responses
  from responses import registries
  import determined
  from determined.common.api import authentication
label_desc: Use image node_id 5 for calling the MockTokenStoreInstance obj's underlying member method code with example usage: obj.drop_user(username) without return types