code: def index_of(self, child):
          
  
          for i, item in enumerate(self.__children):
              if child is item:
                  return i
docs: Returns the given child index.
  
          Usage::
  
              >>> node_a = AbstractCompositeNode("MyNodeA")
              >>> node_b = AbstractCompositeNode("MyNodeB", node_a)
              >>> node_c = AbstractCompositeNode("MyNodeC", node_a)
              >>> node_a.index_of(node_b)
              0
              >>> node_a.index_of(node_c)
              1
  
          :param child: Child node.
          :type child: AbstractNode or AbstractCompositeNode or Object
          :return: Child index.
          :rtype: int