class_docstr: Patch pygac.
docstr: Patch GACLACFile.
code: def setUp(self):
      """Patch GACLACFile."""
      super().setUp()
  
      # Import GACLACFile here to make it patchable. Otherwise self._get_fh
      # might import it first which would prevent a successful patch.
      from satpy.readers.avhrr_l1b_gaclac import GACLACFile
  
      self.GACLACFile = GACLACFile
  
imports: from datetime import datetime
  from unittest import TestCase, mock
  import dask.array
  import numpy
  import pytest
  import xarray
label_desc: Use image node_id 1 for calling the GACLACFilePatcher obj's underlying member method code with example usage: obj.setUp() without return types