sanitize_meta( string $meta_key, mixed $meta_value, string $object_type,  $object_subtype = '' )

function sanitize_meta( $meta_key, $meta_value, $object_type, $object_subtype = '' ) {
	if ( ! empty( $object_subtype ) && has_filter( "sanitize_{$object_type}_meta_{$meta_key}_for_{$object_subtype}" ) ) {

		/**
		 * Filters the sanitization of a specific meta key of a specific meta type and subtype.
		 *
		 * The dynamic portions of the hook name, `$object_type`, `$meta_key`,
		 * and `$object_subtype`, refer to the metadata object type (comment, post, term or user),
		 * the meta key value, and the object subtype respectively.
		 *
		 * @since WP-4.9.8
		 *
		 * @param mixed  $meta_value     Meta value to sanitize.
		 * @param string $meta_key       Meta key.
		 * @param string $object_type    Object type.
		 * @param string $object_subtype Object subtype.
		 */
		return apply_filters( "sanitize_{$object_type}_meta_{$meta_key}_for_{$object_subtype}", $meta_value, $meta_key, $object_type, $object_subtype );
	}

	/**
	 * Filters the sanitization of a specific meta key of a specific meta type.
	 *
	 * The dynamic portions of the hook name, `$meta_type`, and `$meta_key`,
	 * refer to the metadata object type (comment, post, term, or user) and the meta
	 * key value, respectively.
	 *
	 * @since WP-3.3.0
	 *
	 * @param mixed  $meta_value      Meta value to sanitize.
	 * @param string $meta_key        Meta key.
	 * @param string $object_type     Object type.
	 */
	return apply_filters( "sanitize_{$object_type}_meta_{$meta_key}", $meta_value, $meta_key, $object_type );
}