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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def arrows(self):
 """ 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. """

        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())