code: function(opt_paramIds) {
      var container = document.createElement('mutation');
      if (opt_paramIds) {
        container.setAttribute('name', this.getFieldValue('NAME'));
      }
      for (var i = 0; i < this.arguments_.length; i++) {
        var parameter = document.createElement('arg');
        parameter.setAttribute('name', this.arguments_[i]);
        if (opt_paramIds && this.paramIds_) {
          parameter.setAttribute('paramId', this.paramIds_[i]);
        }
        container.appendChild(parameter);
      }
  
      // Save whether the statement input is visible.
      if (!this.hasStatements_) {
        container.setAttribute('statements', 'false');
      }
      return container;
    }
docs: Create XML to represent the argument inputs.
  @param {=boolean} opt_paramIds If true include the IDs of the parameter
  quarks.  Used by Blockly.Procedures.mutateCallers for reconnection.
  @return {!Element} XML storage element.
  @this Blockly.Block