Traceback (most recent call last):
  File "C:\Users\nehad\Desktop\Neha\Non-School\Python\Handwritten Digits 
 Recognition.py", line 38, in <module>
  X_train, y_train, X_test, y_test = load_dataset()
 TypeError: cannot unpack non-iterable NoneType object

import numpy as np
 
 
 def load_dataset():
  def download(filename, source="http://yaan.lecun.com/exdb/mnist/"):
  print ("Downloading ",filename)
  import urllib
  urllib.urlretrieve(source+filename,filename)
 
  import gzip
  
  def load_mnist_images(filename):
  if not os.path.exists(filename):
  download(filename)
  with gzip.open(filename,"rb") as f:
  data=np.frombuffer(f.read(), np.uint8, offset=16)
  
  data = data.reshape(-1,1,28,28)
  
  return data/np.float32(256)
 
  def load_mnist_labels(filename):
  if not os.path.exists(filename):
  download(filename)
  with gzip.open(filename,"rb") as f:
  data = np.frombuffer(f.read(), np.uint8, offset=8)
  return data
 
  X_train = load_mnist_images("train-images-idx3-ubyte.gz")
  y_train = load_mnist_labels("train-labels-idx1-ubyte.gz")
  X_test = load_mnist_images("t10k-images-idx3-ubyte.gz")
  y_test = load_mnist_labels("t10k-labels-idx1-ubyte.gz")
 
  return X_train, y_train, X_test, y_test
 
 
 X_train, y_train, X_test, y_test = load_dataset()
 
 
 import matplotlib
 matplotlib.use("TkAgg")
 
 import matplotlib.pyplot as plt
 plt.show(plt.imshow(X_train[3][0]))