class_docstr: SEVIRI native format reader.
  
  **Calibration**
  
  See :mod:`satpy.readers.seviri_base`.
  
  **Padding channel data to full disk**
  
  By providing the `fill_disk` as True in the `reader_kwargs`, the channel is loaded
  as full disk, padded with no-data where necessary. This is especially useful for the
  HRV channel, but can also be used for RSS and ROI data. By default, the original,
  unpadded, data are loaded::
  
      scene = satpy.Scene(filenames,
                          reader='seviri_l1b_native',
                          reader_kwargs={'fill_disk': False})
  
  **Metadata**
  
  See :mod:`satpy.readers.seviri_base`.
docstr: Get coefficients for calibration from counts to radiance.
docstr_tok: ["Get","coefficients","for","calibration","from","counts","to","radiance","."]
code: def _get_calib_coefs(self, channel_name):
      """Get coefficients for calibration from counts to radiance."""
      # even though all the channels may not be present in the file,
      # the header does have calibration coefficients for all the channels
      # hence, this channel index needs to refer to full channel list
      band_idx = list(CHANNEL_NAMES.values()).index(channel_name)
  
      coefs_nominal = self.header["15_DATA_HEADER"][
          "RadiometricProcessing"
      ]["Level15ImageCalibration"]
      coefs_gsics = self.header["15_DATA_HEADER"][
          "RadiometricProcessing"
      ]["MPEFCalFeedback"]
      radiance_types = self.header["15_DATA_HEADER"][
          "ImageDescription"
      ]["Level15ImageProduction"]["PlannedChanProcessing"]
      return create_coef_dict(
          coefs_nominal=(
              coefs_nominal["CalSlope"][band_idx],
              coefs_nominal["CalOffset"][band_idx],
          ),
          coefs_gsics=(
              coefs_gsics["GSICSCalCoeff"][band_idx],
              coefs_gsics["GSICSOffsetCount"][band_idx],
          ),
          ext_coefs=self.ext_calib_coefs.get(channel_name, {}),
          radiance_type=radiance_types[band_idx],
      )
  
imports: import logging
  import warnings
  from datetime import datetime, timedelta
  import dask.array
  import numpy
  import xarray
  from pyresample import geometry
  from satpy._compat import cached_property
  from satpy.readers._geos_area import get_area_definition, get_geos_area_naming
  from satpy.readers.eum_base import get_service_mode, recarray2dict, time_cds_short
  from satpy.readers.file_handlers import BaseFileHandler
  from satpy.readers.seviri_base import CHANNEL_NAMES, HRV_NUM_COLUMNS, HRV_NUM_LINES, REPEAT_CYCLE_DURATION, SATNUM, VISIR_NUM_COLUMNS, VISIR_NUM_LINES, NoValidOrbitParams, OrbitPolynomialFinder, SEVIRICalibrationHandler, add_scanline_acq_time, calculate_area_extent, create_coef_dict, dec10216, get_cds_time, get_satpos, pad_data_horizontally, pad_data_vertically, round_nom_time
  from satpy.readers.seviri_l1b_native_hdr import DEFAULT_15_SECONDARY_PRODUCT_HEADER, GSDTRecords, get_native_header, native_trailer
  from satpy.readers.utils import reduce_mda
  from satpy.utils import get_legacy_chunk_size
label_desc: Use image node_id 20 for calling the NativeMSGFileHandler obj's underlying member method code with example usage: obj._get_calib_coefs(channel_name) and returns: create_coef_dict