code: function() {
      this.setColour(Blockly.Blocks.logic.HUE);
      this.appendDummyInput()
          .appendField(Blockly.Msg.CONTROLS_IF_IF_TITLE_IF);
      this.setNextStatement(true);
      this.setTooltip(Blockly.Msg.CONTROLS_IF_IF_TOOLTIP);
      this.contextMenu = false;
    }
docs: Mutator block for if container.
  @this Blockly.Block