docstr: Test empty ``emr_conn_id``.
docstr_tok: ["Test","empty","``","emr_conn_id","``","."]
code: def test_empty_emr_conn_id(self, mock_boto3_client):
      """Test empty ``emr_conn_id``."""
      mock_run_job_flow = mock.MagicMock()
      mock_boto3_client.return_value.run_job_flow = mock_run_job_flow
      job_flow_overrides = {"foo": "bar"}
  
      hook = EmrHook(aws_conn_id="aws_default", emr_conn_id=None)
      hook.create_job_flow(job_flow_overrides)
      mock_run_job_flow.assert_called_once_with(**job_flow_overrides)
  
imports: from __future__ import annotations
  import re
  from unittest import mock
  import boto3
  import pytest
  from botocore.exceptions import WaiterError
  from moto import mock_emr
  from airflow.exceptions import AirflowException
  from airflow.providers.amazon.aws.hooks.emr import EmrHook
label_desc: Use image node_id 8 for calling the TestEmrHook obj's underlying member method code with example usage: obj.test_empty_emr_conn_id(mock_boto3_client) without return types