code: def test_frequency_range_class_method_str():
      """Test the frequency range object: test the band description."""
      frq_range1 = FrequencyRange(89, 2)
      frq_range2 = FrequencyRange(89000, 2000, "MHz")
  
      assert str(frq_range1) == "central=89 GHz width=2 GHz"
      assert str(frq_range2) == "central=89000 MHz width=2000 MHz"
  
imports: import unittest
  from datetime import datetime
  import numpy
  import pytest
  from satpy.dataset.dataid import DataID, DataQuery, ModifierTuple, WavelengthRange, minimal_default_keys_config
  from satpy.readers.pmw_channels_definitions import FrequencyDoubleSideBand, FrequencyQuadrupleSideBand, FrequencyRange
  from satpy.tests.utils import make_cid, make_dataid, make_dsq
label_desc: Use image node_id 19 for calling a global function with example usage: test_frequency_range_class_method_str() without return types