class_docstr: Test case for reading calibrated brightness temperature from hrpt data.
class_docstr_tok: ["Test","case","for","reading","calibrated","brightness","temperature","from","hrpt","data","."]
docstr: Test that channel 3b is split correctly.
code: def test_channel_3b_masking(self):
      """Test that channel 3b is split correctly."""
      result = self._get_channel_3b_bt()
      assert np.isnan(result.values[:5]).all()
      assert np.isfinite(result.values[5:]).all()
  
imports: import os
  import unittest
  from contextlib import suppress
  from tempfile import NamedTemporaryFile
  from unittest import mock
  import numpy
  import xarray
  from satpy.readers.hrpt import HRPTFile, dtype
  from satpy.tests.reader_tests.test_avhrr_l1b_gaclac import PygacPatcher
  from satpy.tests.utils import make_dataid
label_desc: Use image node_id 4 for calling the TestHRPTChannel3 obj's underlying member method code with example usage: obj.test_channel_3b_masking() without return types