code: def test_frequency_range_channel_distances():
      """Test the frequency range object: derive distances between bands."""
      frqr = FrequencyRange(190.0, 2)
  
      mydist = frqr.distance(FrequencyRange(190, 2))
      assert mydist == 0
      mydist = frqr.distance(FrequencyRange(189.5, 2))
      assert mydist == np.inf
      mydist = frqr.distance(189.5)
      assert mydist == 0.5
      mydist = frqr.distance(188.0)
      assert mydist == np.inf
  
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 22 for calling a global function with example usage: test_frequency_range_channel_distances() without return types