code: def test_event_metaclass() -> None:
      # All events currently in the namespace should be in the EVENT_CLASSES set
      assert (
          len(
              concrete_events
              - set(events._CONCRETE_EVENT_CLASSES.values())
          )
          == 0
      )
  
imports: from __future__ import annotations
  import pytest
  from bokeh.core.serialization import Deserializer
  from bokeh.models import Button, Div, Plot, TextInput
  from bokeh import events
label_desc: Use image node_id 1 for calling a global function with example usage: test_event_metaclass() without return types