Document.php

<?php
/**
 * Copyright © 2015 Magento. All rights reserved.
 * See COPYING.txt for license details.
 */
namespace Magento\CatalogSearch\Model;

use Magento\CatalogSearch\Api\Data\DocumentInterface;
use Magento\Framework\Api\AbstractSimpleObject;

class Document extends AbstractSimpleObject implements DocumentInterface
{
    /**
     * {@inheritdoc}
     */
    public function getId()
    {
        return $this->_get(self::ID);
    }

    /**
     * {@inheritdoc}
     */
    public function setId($id)
    {
        return $this->_set(self::ID, $id);
    }

    /**
     * {@inheritdoc}
     */
    public function getData()
    {
        $this->_get(self::DATA);
    }

    /**
     * {@inheritdoc}
     */
    public function setData($data)
    {
        return $this->_set(self::DATA, $data);
    }

    /**
     * Set value for the given key
     *
     * @param string $key
     * @param mixed $value
     * @return $this
     */
    protected function _set($key, $value)
    {
        return parent::setData($key, $value);
    }
}