code: def check_answer(self, hash_answer):
          
          for challenge in self.challenges:
              if challenge.response == hash_answer:
                  # If we don't discard a used challenge then a node
                  # could fake having the file because it already
                  # knows the proper response
                  self.delete_challenge(hash_answer)
                  return True
          return False
docs: Check if the returned hash is in our challenges list.
  
          :param hash_answer: Hash that we compare to our list of challenges
          :return: boolean indicating if answer is correct, True, or not, False