Removes a **node object** from the ``DictGraph``. Returns ``True`` if a 
        **node object** has been removed. If the **node object** is not in the
        ``DictGraph`` raises a ``KeyError``.
        
        Arguments:
            
          - node(``object``) **node object** to be removed. Any hashable Python 
            ``object``.

def del_node(self, node):
        """
        Removes a **node object** from the ``DictGraph``. Returns ``True`` if a 
        **node object** has been removed. If the **node object** is not in the
        ``DictGraph`` raises a ``KeyError``.
        
        Arguments:
            
          - node(``object``) **node object** to be removed. Any hashable Python 
            ``object``.
           
        """
        for node_ in self.values():
            if node in node_:
                node_.pop(node)
        return bool(self.pop(node))