code: def test_bool(self):
      gv = pyvips.GValue()
      gv.set_type(pyvips.GValue.gbool_type)
      gv.set(True)
      value = gv.get()
      assert value
  
      gv.set(False)
      value = gv.get()
      assert not value
  
file_path: pyvips/tests/test_gvalue.py
imports: import pytest
  import pyvips
  from helpers import JPEG_FILE, assert_almost_equal_objects
label_desc: Use image node_id 1 for calling the TestGValue obj's underlying member method code with example usage: obj.test_bool() without return types