code: def arrows(self):
          
          if self.active_vectors is None:
              return
  
          arrow = vtk.vtkArrowSource()
          arrow.Update()
  
          alg = vtk.vtkGlyph3D()
          alg.SetSourceData(arrow.GetOutput())
          alg.SetOrient(True)
          alg.SetInputData(self)
          alg.SetVectorModeToUseVector()
          alg.SetScaleModeToScaleByVector()
          alg.Update()
          return vtki.wrap(alg.GetOutput())
docs: Returns a glyph representation of the active vector data as
          arrows.  Arrows will be located at the points of the mesh and
          their size will be dependent on the length of the vector.
          Their direction will be the "direction" of the vector
  
          Returns
          -------
          arrows : vtki.PolyData
              Active scalars represented as arrows.