code: def combine(self, merge_points=False):
          
          alg = vtk.vtkAppendFilter()
          for block in self:
              alg.AddInputData(block)
          alg.SetMergePoints(merge_points)
          alg.Update()
          return wrap(alg.GetOutputDataObject(0))
docs: Appends all blocks into a single unstructured grid.
  
          Parameters
          ----------
          merge_points : bool, optional
              Merge coincidental points.