code: def set_attrs(self, username, attrs):
          
          self._check_fix_users(username)
          for attr in attrs:
              self.users[username][attr] = attrs[attr]
docs: set a list of attributes for a given user
  
          :param username: 'key' attribute of the user
          :type username: string
          :param attrs: attributes of the user
          :type attrs: dict ({<attr>: <value>})