class_docstr: Unit tests for SEVIRI calibration handler.
class_docstr_tok: ["Unit","tests","for","SEVIRI","calibration","handler","."]
docstr: Provide a calibration handler.
docstr_tok: ["Provide","a","calibration","handler","."]
code: def _get_calibration_handler(
      self, calib_mode="NOMINAL", ext_coefs=None
  ):
      """Provide a calibration handler."""
      return SEVIRICalibrationHandler(
          platform_id=324,
          channel_name="IR_108",
          coefs={
              "coefs": {
                  "NOMINAL": {"gain": 10, "offset": -1},
                  "GSICS": {"gain": 20, "offset": -2},
                  "EXTERNAL": ext_coefs or {},
              },
              "radiance_type": 1,
          },
          calib_mode=calib_mode,
          scan_time=None,
      )
  
imports: import unittest
  from datetime import datetime
  import numpy
  import pytest
  import xarray
  from satpy.readers.seviri_base import SEVIRICalibrationAlgorithm, SEVIRICalibrationHandler
label_desc: Use image node_id 2 for calling the TestSeviriCalibrationHandler obj's underlying member method code with example usage: obj._get_calibration_handler(calib_mode, ext_coefs) and returns: SEVIRICalibrationHandler