code: def create_nwcsaf_geo_ct_file(directory, attrs=global_attrs_geo):
      """Create a CT file."""
      filename = (
          directory
          / "S_NWC_CT_MSG4_MSG-N-VISIR_20230118T103000Z_PLAX.nc"
      )
      with h5netcdf.File(filename, mode="w") as nc_file:
          nc_file.dimensions = dimensions
          nc_file.attrs.update(attrs)
          var_name = "ct"
  
          var = nc_file.create_variable(
              var_name, ("ny", "nx"), np.uint16, chunks=(256, 256)
          )
          var[:] = np.random.randint(
              0, 255, size=(928, 1530), dtype=np.uint8
          )
  
      return filename
  
imports: import h5netcdf
  import numpy
  import pytest
  import xarray
  from satpy.readers.nwcsaf_nc import NcNWCSAF, read_nwcsaf_time
label_desc: Use image node_id 2 for calling a global function with example usage: create_nwcsaf_geo_ct_file(directory, attrs) and returns: filename