code: def test_multi_block_volume(ant, airplane, sphere, uniform):
      multi = multi_from_datasets(ant, sphere, uniform, airplane, None)
      vols = (
          ant.volume + sphere.volume + uniform.volume + airplane.volume
      )
      assert multi.volume == pytest.approx(vols)
  
imports: import pathlib
  import platform
  import weakref
  import numpy
  import pytest
  import vtk
  import pyvista
  from pyvista import ImageData, MultiBlock, PolyData, RectilinearGrid, StructuredGrid, examples
label_desc: Use image node_id 29 for calling a global function with example usage: test_multi_block_volume(ant, airplane, sphere, uniform) without return types