protected $model_post_type = 'certificate';

	/**
	 * Object properties
	 *
	 * @var array
	 */
	protected $properties = array(
		'allow_sharing' => 'string',
		'awarded'       => 'string',
		'background'    => 'string',
		'engagement'    => 'absint',
		'height'        => 'float',
		'margins'       => 'array',
		'orientation'   => 'string',
		'related'       => 'absint',
		'sequential_id' => 'absint',
		'size'          => 'string',
		'unit'          => 'string',
		'width'         => 'float',
	);

	/**
	 * Array of default property values.
	 *
	 * In the form of key => default value.
	 *
	 * @var array
	 */
	protected $property_defaults = array(
		'background'    => '#ffffff',
		'orientation'   => 'landscape',
		'margins'       => array( 5, 5, 5, 5 ),
		'sequential_id' => 1,