code: def test_test_manual_background():
      """Test manual background"""
      workspace, x = make_workspace(numpy.zeros((10, 10)))
      x = cellprofiler.modules.threshold.Threshold()
      x.threshold_scope.value = cellprofiler.modules.threshold.TS_GLOBAL
      x.global_operation.value = (
          cellprofiler.modules.threshold.TM_MANUAL
      )
      x.manual_threshold.value = 0.5
      local_threshold, threshold, _, _, _ = x.get_threshold(
          cellprofiler_core.image.Image(
              numpy.zeros((10, 10)), mask=numpy.ones((10, 10), bool)
          ),
          workspace,
      )
      assert threshold == 0.5
      assert threshold == 0.5
  
imports: import io
  import centrosome.filter
  import centrosome.otsu
  import centrosome.threshold
  import numpy
  import numpy.testing
  import skimage.filters
  import skimage.filters.rank
  import skimage.morphology
  import cellprofiler.modules.threshold
  import cellprofiler_core.image
  import cellprofiler_core.measurement
  import cellprofiler_core.module
  import cellprofiler_core.object
  import cellprofiler_core.pipeline
  import cellprofiler_core.preferences
  import cellprofiler_core.workspace
  from cellprofiler_core.constants.measurement import FF_ORIG_THRESHOLD
  from cellprofiler_core.constants.module._identify import TS_GLOBAL
  import cellprofiler_library.modules
  import cellprofiler_library.functions
  import tests.frontend.modules
label_desc: Use image node_id 19 for calling a global function with example usage: test_test_manual_background() without return types