code: def _create_mcmip_dataset():
      ds1 = _create_cmip_dataset("CMI_C01")
      ds2 = _create_cmip_dataset("CMI_C14")
      ds1["CMI_C01"].attrs["units"] = "1"
      ds2["CMI_C14"].attrs["units"] = "K"
      ds1["CMI_C14"] = ds2["CMI_C14"]
      return ds1
  
imports: import contextlib
  from typing import Optional
  from unittest import mock
  import numpy
  import pytest
  import xarray
label_desc: Use image node_id 4 for calling a global function with example usage: _create_mcmip_dataset() and returns: ds1