code: def test_color(block_attr):
      # when unset this must be None
      assert block_attr.color is None
  
      color = "red"
      block_attr.color = color
      assert block_attr.color == pv.Color(color).float_rgb
  
      color = (1, 1, 0)
      block_attr.color = color
      assert block_attr.color == pv.Color(color).float_rgb
  
      block_attr.color = None
      assert block_attr.color is None
  
imports: import pytest
  from vtkmodules.vtkCommonCore import vtkLookupTable
  import pyvista
  from pyvista.plotting.composite_mapper import BlockAttributes, CompositePolyDataMapper
label_desc: Use image node_id 16 for calling a global function with example usage: test_color(block_attr) without return types