code: def test_returns_none_if_server_version_is_none(
      self, client_version: Optional[str]
  ):
      assert (
          check_client_server_compatibility(
              client_version=client_version,
              server_version=None,
          )
          is None
      )
  
file_path: dstack/src/tests/_internal/server/utils/test_routers.py
imports: from typing import Optional
  import pytest
  from dstack._internal.server.utils.routers import check_client_server_compatibility
label_desc: Use image node_id 1 for calling the TestCheckClientServerCompatibility obj's underlying member method code with example usage: obj.test_returns_none_if_server_version_is_none(client_version) without return types