docs: def show_edge(self, edge_id):
          """Displays edge with ce_ratio.
  
          :param edge_id: Edge ID for which to show the ce_ratio.
          :type edge_id: int
          """
          # pylint: disable=unused-variable,relative-import
          from mpl_toolkits.mplot3d import Axes3D
          from matplotlib import pyplot as plt
  
          if "faces" not in self.cells:
              self.create_cell_face_relationships()
          if "edges" not in self.faces:
              self.create_face_edge_relationships()
  
          fig = plt.figure()
          ax = fig.gca(projection=Axes3D.name)
          plt.axis("equal")
  
          # find all faces with this edge
          adj_face_ids = numpy.where((self.faces["edges"] == edge_id).any(axis=1))[0]
          # find all cells with the faces
          # https://stackoverflow.com/a/38481969/353337
          adj_cell_ids = numpy.where(
              numpy.in1d(self.cells["faces"], adj_face_ids)
              .reshape(self.cells["faces"].shape)
              .any(axis=1)
          )[0]
  
          # plot all those adjacent cells; first collect all edges
          adj_edge_ids = numpy.unique(
              [
                  adj_edge_id
                  for adj_cell_id in adj_cell_ids
                  for face_id in self.cells["faces"][adj_cell_id]
                  for adj_edge_id in self.faces["edges"][face_id]
              ]
          )
          col = "k"
          for adj_edge_id in adj_edge_ids:
              x = self.node_coords[self.edges["nodes"][adj_edge_id]]
              ax.plot(x[:, 0], x[:, 1], x[:, 2], col)
  
          # make clear which is edge_id
          x = self.node_coords[self.edges["nodes"][edge_id]]
          ax.plot(x[:, 0], x[:, 1], x[:, 2], color=col, linewidth=3.0)
  
          # connect the face circumcenters with the corresponding cell
          # circumcenters
          X = self.node_coords
          for cell_id in adj_cell_ids:
              cc = self._circumcenters[cell_id]
              #
              x = X[self.node_face_cells[..., [cell_id]]]
              face_ccs = compute_triangle_circumcenters(x, self.ei_dot_ei, self.ei_dot_ej)
              # draw the face circumcenters
              ax.plot(
                  face_ccs[..., 0].flatten(),
                  face_ccs[..., 1].flatten(),
                  face_ccs[..., 2].flatten(),
                  "go",
              )
              # draw the connections
              #   tet circumcenter---face circumcenter
              for face_cc in face_ccs:
                  ax.plot(
                      [cc[..., 0], face_cc[..., 0]],
                      [cc[..., 1], face_cc[..., 1]],
                      [cc[..., 2], face_cc[..., 2]],
                      "b-",
                  )
  
          # draw the cell circumcenters
          cc = self._circumcenters[adj_cell_ids]
          ax.plot(cc[:, 0], cc[:, 1], cc[:, 2], "ro")
          return