code: def plot_pauli_transfer_matrix(ptransfermatrix, ax, labels, title):
      
      im = ax.imshow(ptransfermatrix, interpolation="nearest", cmap=rigetti_3_color_cm, vmin=-1,
                     vmax=1)
      dim = len(labels)
      plt.colorbar(im, ax=ax)
      ax.set_xticks(range(dim))
      ax.set_xlabel("Input Pauli Operator", fontsize=20)
      ax.set_yticks(range(dim))
      ax.set_ylabel("Output Pauli Operator", fontsize=20)
      ax.set_title(title, fontsize=25)
      ax.set_xticklabels(labels, rotation=45)
      ax.set_yticklabels(labels)
      ax.grid(False)
      return ax
docs: Visualize the Pauli Transfer Matrix of a process.
  
      :param numpy.ndarray ptransfermatrix: The Pauli Transfer Matrix
      :param ax: The matplotlib axes.
      :param labels: The labels for the operator basis states.
      :param title: The title for the plot
      :return: The modified axis object.
      :rtype: AxesSubplot