code: def del_node(self, node):
          
          if self.has_node(node):
              for e in self.node_links[node]:
                  self.edge_links[e].remove(node)
  
              self.node_links.pop(node)
              self.graph.del_node((node,'n'))
docs: Delete a given node from the hypergraph.
          
          @type  node: node
          @param node: Node identifier.