public function update_notification( $id, $content = null, $type = null, $hide_button = null, $cond_func = null ) {
        if ( ! isset( $this->notices[$id] ) ) {
            $this->add_notification( $id, $content, $type, $hide_button, $cond_func );	
        }	

        if ( $content ) {
            $this->notices[$id]['content'] = $content;
        }

        if ( $type ) {
            $this->notices[$id]['type'] = $type;
        }

        if ( $hide_button ) {
            $this->notices[$id]['hide_button'] = $hide_button;
        }

        if ( $cond_func ) {
            $this->notices[$id]['cond_func'] = $cond_func;
        }

        $this->save();
    }