class_docstr: Test the AHI gridded reader definition.
docstr: Create a test file handler.
docstr_tok: ["Create","a","test","file","handler","."]
code: def make_fh(filetype, area="fld"):
      """Create a test file handler."""
      m = mock.mock_open()
      with mock.patch(
          "satpy.readers.ahi_l1b_gridded_bin.open", m, create=True
      ):
          fh = AHIGriddedFileHandler(
              "somefile",
              {"area": area},
              filetype_info={"file_type": filetype},
          )
          return fh
  
imports: import os
  import shutil
  import tempfile
  import unittest
  from unittest import mock
  import dask.array
  import numpy
  import pytest
  from pyresample.geometry import AreaDefinition
  from satpy.readers.ahi_l1b_gridded_bin import AHI_LUT_NAMES, AHIGriddedFileHandler
label_desc: Use image node_id 2 for calling the TestAHIGriddedArea obj's underlying member method code with example usage: obj.make_fh(filetype, area) and returns: fh