code: def init(app_id, app_key=None, master_key=None, hook_key=None):
      
      if (not app_key) and (not master_key):
          raise RuntimeError('app_key or master_key must be specified')
      global APP_ID, APP_KEY, MASTER_KEY, HOOK_KEY
      APP_ID = app_id
      APP_KEY = app_key
      MASTER_KEY = master_key
      if hook_key:
          HOOK_KEY = hook_key
      else:
          HOOK_KEY = os.environ.get('LEANCLOUD_APP_HOOK_KEY')
docs: 初始化 LeanCloud 的 AppId / AppKey / MasterKey
  
      :type app_id: string_types
      :param app_id: 应用的 Application ID
      :type app_key: None or string_types
      :param app_key: 应用的 Application Key
      :type master_key: None or string_types
      :param master_key: 应用的 Master Key
      :param hook_key: application's hook key
      :type hook_key: None or string_type