old_contents: #-*- coding: utf-8 -*-
  
  class GithubAccount:
      def __init__(self, username, password):
          self.username = username
          self.password = password
  
  class GithubAPI:
      def __init__(self, account):
          self.account = account
  
new_contents: #-*- coding: utf-8 -*-
  
  class GithubAccount:
      def __init__(self, username, password):
          self.username = username
          self.password = password
          if not self.is_valid():
              raise ValueError('Account is invalid. Username or password is incorrect.')
          
      def is_valid(self):
          import requests
          r = requests.get('https://api.github.com/notifications', 
              auth = (self.username, self.password))
          if r.status_code == 401: # Not Authorized
              return False
          return True
  
  class GithubAPI:
      def __init__(self, account):
          self.account = account
  
subject: fix #6. check validation of GithubAccount.