code: def test_send_callback(self):
      cel_exec = CeleryExecutor()
      k8s_exec = KubernetesExecutor()
      cel_k8s_exec = CeleryKubernetesExecutor(cel_exec, k8s_exec)
      cel_k8s_exec.callback_sink = mock.MagicMock()
  
      callback = CallbackRequest(full_filepath="fake")
      cel_k8s_exec.send_callback(callback)
  
      cel_k8s_exec.callback_sink.send.assert_called_once_with(callback)
  
imports: from __future__ import annotations
  from unittest import mock
  import pytest
  from airflow.callbacks.callback_requests import CallbackRequest
  from airflow.configuration import conf
  from airflow.providers.celery.executors.celery_executor import CeleryExecutor
  from airflow.providers.celery.executors.celery_kubernetes_executor import CeleryKubernetesExecutor
  from airflow.providers.cncf.kubernetes.executors.kubernetes_executor import KubernetesExecutor
label_desc: Use image node_id 21 for calling the TestCeleryKubernetesExecutor obj's underlying member method code with example usage: obj.test_send_callback() without return types