WP_Image_Editor choosing implementation

gistfile1.php

<?php

class WP_Image_Editor {

	final public static function get_instance( $path ) {
		$implementation = apply_filters( 'image_editor_class', self::choose_implementation(), $path );

		if ( $implementation )
			return new $implementation( $path );

		return false;
	}

	// Chooses the best available image handling library available
	private static function choose_implementation() {
		static $implementation;

		if ( null === $implementation ) {
			// actual logic for setting $implementation goes here

			...
		}

		return $implementation;
	}

	...
}