code: def sinwave(scene):
      
      # create an empty homogenous transformation
      matrix = np.eye(4)
      # set Y as cos of time
      matrix[1][3] = np.cos(time.time()) * 2
      # set Z as sin of time
      matrix[2][3] = np.sin(time.time()) * 3
  
      # take one of the two spheres arbitrarily
      node = s.graph.nodes_geometry[0]
      # apply the transform to the node
      scene.graph.update(node, matrix=matrix)
docs: A callback passed to a scene viewer which will update
      transforms in the viewer periodically.
  
      Parameters
      -------------
      scene : trimesh.Scene
        Scene containing geometry