clone(parent) {
    var clone = super.clone(parent);
    clone.map = {};
    for (var key in this.map) {
      clone.map[key] = this.map[key].clone(parent, clone);
    }
    clone.isList = this.isList;
    clone.lineno = this.lineno;
    clone.column = this.column;
    clone.filename = this.filename;
    return clone;
  }
Return a clone of this node.

@return {Node}
@api public