code: def del_node(self, node):
          
          for node_ in self.values():
              if node in node_:
                  node_.pop(node)
          return bool(self.pop(node))
docs: 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``.