code: def edge_mask(self, angle):
          
          self.point_arrays['point_ind'] = np.arange(self.n_points)
          featureEdges = vtk.vtkFeatureEdges()
          featureEdges.SetInputData(self)
          featureEdges.FeatureEdgesOn()
          featureEdges.BoundaryEdgesOff()
          featureEdges.NonManifoldEdgesOff()
          featureEdges.ManifoldEdgesOff()
          featureEdges.SetFeatureAngle(angle)
          featureEdges.Update()
          edges = _get_output(featureEdges)
          orig_id = vtki.point_scalar(edges, 'point_ind')
  
          return np.in1d(self.point_arrays['point_ind'], orig_id,
                         assume_unique=True)
docs: Returns a mask of the points of a surface mesh that have a surface
          angle greater than angle
  
          Parameters
          ----------
          angle : float
              Angle to consider an edge.