Source

File: wp-includes/class-wp-site-query.php

public function parse_query( $query = '' ) {
		if ( empty( $query ) ) {
			$query = $this->query_vars;
		}

		$this->query_vars = wp_parse_args( $query, $this->query_var_defaults );

		/**
		 * Fires after the site query vars have been parsed.
		 *
		 * @since 4.6.0
		 *
		 * @param WP_Site_Query $this The WP_Site_Query instance (passed by reference).
		 */
		do_action_ref_array( 'parse_site_query', array( &$this ) );
	}