function column_cb( $item ) {
		return sprintf(
			'<input type="checkbox" name="%1$s[]" value="%2$s" />',
			/*$1%s*/ $this->_args['singular'],  //Let's simply repurpose the table's singular label ("instructor")
			/*$2%s*/ $item->ID                //The value of the checkbox should be the record's id
		);
	}