code: def del_node(self, node):
          
          for each in list(self.incidents(node)):
              # Delete all the edges incident on this node
              self.del_edge((each, node))
              
          for each in list(self.neighbors(node)):
              # Delete all the edges pointing to this node.
              self.del_edge((node, each))
          
          # Remove this node from the neighbors and incidents tables   
          del(self.node_neighbors[node])
          del(self.node_incidence[node])
          
          # Remove any labeling which may exist.
          self.del_node_labeling( node )
docs: Remove a node from the graph.
          
          @type  node: node
          @param node: Node identifier.