public static function get_class_name( $field ) {
$type = self::map_types( $field );
$type = str_replace( array( '-', '_' ), ' ', $type );
$class = 'RWMB_' . ucwords( $type ) . '_Field';
$class = str_replace( ' ', '_', $class );
return class_exists( $class ) ? $class : 'RWMB_Input_Field';
}