code: def plot(self, show_holes=True):
          
          if show_holes:
              edges = self.mesh.extract_edges(boundary_edges=True,
                                              feature_edges=False,
                                              manifold_edges=False)
  
              plotter = vtki.Plotter()
              plotter.add_mesh(self.mesh, label='mesh')
              plotter.add_mesh(edges, 'r', label='edges')
              plotter.plot()
  
          else:
              self.mesh.plot(show_edges=True)
docs: Plot the mesh.
  
          Parameters
          ----------
          show_holes : bool, optional
              Shows boundaries.  Default True