code: def has_child(self, child):
          
          if u'children' not in self:
              return False
  
          if not isinstance(child, basestring):
              child = child.get_id()
  
          return child in self.children
docs: Checks if the given child id
          :param child: The id to check if it's a child of the group
          :return: True if the given id it's a child of this group, False otherwise