Collection.php

<?php
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
namespace Magento\Newsletter\Model\ResourceModel\Template;

/**
 * Newsletter templates collection
 *
 * @author      Magento Core Team <core@magentocommerce.com>
 *
 * @api
 * @since 100.0.2
 */
class Collection extends \Magento\Framework\Model\ResourceModel\Db\Collection\AbstractCollection
{
    /**
     * Define resource model and model
     *
     * @return void
     */
    protected function _construct()
    {
        $this->_init(
            \Magento\Newsletter\Model\Template::class,
            \Magento\Newsletter\Model\ResourceModel\Template::class
        );
    }

    /**
     * Load only actual template
     *
     * @return $this
     */
    public function useOnlyActual()
    {
        $this->addFieldToFilter('template_actual', 1);

        return $this;
    }

    /**
     * Returns options array
     *
     * @return array
     */
    public function toOptionArray()
    {
        return $this->_toOptionArray('template_id', 'template_code');
    }
}