*
	 * @param WP_REST_Request $request Request object.
	 * @return array|WP_Error Array of llms post args or WP_Error.
	 */
	protected function prepare_item_for_database( $request ) {

		$prepared_item = parent::prepare_item_for_database( $request );

		$schema = $this->get_item_schema();

		// LLMS Section parent id.
		if ( ! empty( $schema['properties']['parent_id'] ) && isset( $request['parent_id'] ) ) {

			$parent_course = llms_get_post( $request['parent_id'] );

			if ( ! $parent_course || ! is_a( $parent_course, 'LLMS_Course' ) ) {
				return llms_rest_bad_request_error( __( 'Invalid parent_id param. It must be a valid Course ID.', 'lifterlms' ) );
			}

			$prepared_item['parent_course'] = $request['parent_id'];
		}

		// LLMS Section order.
		if ( ! empty( $schema['properties']['order'] ) && isset( $request['order'] ) ) {

			// order must be > 0. It's sanitized as absint so it cannot come as negative value.
			if ( 0 === $request['order'] ) {
				return llms_rest_bad_request_error( __( 'Invalid order param. It must be greater than 0.', 'lifterlms' ) );
			}

			$prepared_item['order'] = $request['order'];
		}