code: def verify_notification(data):
      
      pemfile = grab_keyfile(data['SigningCertURL'])
      cert = crypto.load_certificate(crypto.FILETYPE_PEM, pemfile)
      signature = base64.decodestring(six.b(data['Signature']))
  
      if data['Type'] == "Notification":
          hash_format = NOTIFICATION_HASH_FORMAT
      else:
          hash_format = SUBSCRIPTION_HASH_FORMAT
  
      try:
          crypto.verify(
              cert, signature, six.b(hash_format.format(**data)), 'sha1')
      except crypto.Error:
          return False
      return True
docs: Function to verify notification came from a trusted source
  
      Returns True if verfied, False if not verified