code: def plot_two_digit_freqs(f2):
      """
      Plot two digits frequency counts using matplotlib.
      """
      f2_copy = f2.copy()
      f2_copy.shape = (10, 10)
      ax = plt.matshow(f2_copy)
      plt.colorbar()
      for i in range(10):
          for j in range(10):
              plt.text(i - 0.2, j + 0.2, str(j) + str(i))
      plt.ylabel("First digit")
      plt.xlabel("Second digit")
      return ax
  
file_path: ipyparallel/examples/pi/pidigits.py
imports: import os
  from urllib.request import urlretrieve
  import numpy
  from matplotlib import pyplot
label_desc: Use image node_id 10 for calling a global function with example usage: plot_two_digit_freqs(f2) and returns: ax