code: def insat_filehandler(insat_filename):
      """Instantiate a Filehandler."""
      fileinfo = {}
      filetype = None
      fh = Insat3DIMGL1BH5FileHandler(
          insat_filename, fileinfo, filetype
      )
      return fh
  
imports: import os
  from datetime import datetime
  import dask.array
  import h5netcdf
  import numpy
  import pytest
  from satpy import Scene
  from satpy.readers.insat3d_img_l1b_h5 import CHANNELS_BY_RESOLUTION, LUT_SUFFIXES, Insat3DIMGL1BH5FileHandler, get_lonlat_suffix, open_dataset, open_datatree
  from satpy.tests.utils import make_dataid
label_desc: Use image node_id 17 for calling a global function with example usage: insat_filehandler(insat_filename) and returns: fh