code: def test_use_circular_splat(mapper):
      mapper.use_circular_splat()
      assert "offsetVCVSOutput" in mapper.GetSplatShaderCode()
  
      mapper.use_default_splat()
      assert mapper.GetSplatShaderCode() is None
  
file_path: pyvista/tests/plotting/mappers/test_gaussian_mapper.py
imports: import pytest
  import pyvista
  from pyvista.plotting.mapper import PointGaussianMapper
label_desc: Use image node_id 6 for calling a global function with example usage: test_use_circular_splat(mapper) without return types