function parseNodeStatement(graph, id) {
  // node statement
  var node = {
    id: id,
  };
  var attr = parseAttributeList();
  if (attr) {
    node.attr = attr;
  }
  addNode(graph, node);

  // edge statements
  parseEdge(graph, id);
}
parse a node statement
@param {object} graph
@param {string | number} id