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function is not described

rest_handle_deprecated_function() WP 4.4.0

Handles _deprecated_function() errors.

No Hooks.

Return

Nothing (null).

Usage

rest_handle_deprecated_function( $function, $replacement, $version );
$function(string) (required)
The function that was called.
$replacement(string) (required)
The function that should have been called.
$version(string) (required)
Version.

Code of rest handle deprecated function: wp-includes/rest-api.php WP 5.2.2

<?php
function rest_handle_deprecated_function( $function, $replacement, $version ) {
	if ( ! WP_DEBUG || headers_sent() ) {
		return;
	}
	if ( ! empty( $replacement ) ) {
		/* translators: 1: function name, 2: WordPress version number, 3: new function name */
		$string = sprintf( __( '%1$s (since %2$s; use %3$s instead)' ), $function, $version, $replacement );
	} else {
		/* translators: 1: function name, 2: WordPress version number */
		$string = sprintf( __( '%1$s (since %2$s; no alternative available)' ), $function, $version );
	}

	header( sprintf( 'X-WP-DeprecatedFunction: %s', $string ) );
}