code: function() {
      var container = document.createElement('mutation');
      container.setAttribute('name', this.getProcedureCall());
      for (var i = 0; i < this.arguments_.length; i++) {
        var parameter = document.createElement('arg');
        parameter.setAttribute('name', this.arguments_[i]);
        container.appendChild(parameter);
      }
      return container;
    }
docs: Create XML to represent the (non-editable) name and arguments.
  @return {!Element} XML storage element.
  @this Blockly.Block