WordPress at a glance
function is not described

SimplePie::set_image_handler() public WP 1.0

Set the handler to enable the display of cached images.

{} It's a method of the class: SimplePie{}

No Hooks.

Return

null. Nothing.

Usage

$SimplePie = new SimplePie();
$SimplePie->set_image_handler( $page, $qs );
$page(string)
Web-accessible path to the handler_image.php file.
$qs(string)
The query string that the value should be passed to.

Code of SimplePie::set_image_handler() WP 5.7.2

<?php
public function set_image_handler($page = false, $qs = 'i')
{
	if ($page !== false)
	{
		$this->sanitize->set_image_handler($page . '?' . $qs . '=');
	}
	else
	{
		$this->image_handler = '';
	}
}