public function remove_filter($tag, $function_to_remove, $priority = 10)
    {
        $function_to_remove = self::_filter_build_unique_id($tag, $function_to_remove, $priority);

        $r = isset($$this->filter[ $tag ][ $priority ][ $function_to_remove ]);

        if (true === $r) {
            unset($this->filter[ $tag ][ $priority ][ $function_to_remove ]);
            if (empty($this->filter[ $tag ][ $priority ])) {
                unset($this->filter[ $tag ][ $priority ]);
            }
            if (empty($this->filter[ $tag ])) {
                $this->filter[ $tag ] = array();
            }
            unset($this->merged_filters[ $tag ]);
        }

        return $r;
    }