code: function() {
      this.setColour(160);
      this.appendDummyInput()
          .appendField('variable')
          .appendField(new Blockly.FieldTextInput('item'), 'TEXT')
          .appendField(',')
          .appendField(new Blockly.FieldTextInput('NAME'), 'FIELDNAME');
      this.setPreviousStatement(true, 'Field');
      this.setNextStatement(true, 'Field');
      this.setTooltip('Dropdown menu for variable names.');
      this.setHelpUrl('https://www.youtube.com/watch?v=s2_xaEvcVI0#t=510');
    }
docs: Dropdown for variables.