def grouped_t(wrap, size):
    """
    Transformation for Sequence.grouped
    :param wrap: wrap children values with this
    :param size: size of groups
    :return: transformation
    """
    return Transformation(
        'grouped({0})'.format(size),
        partial(grouped_impl, wrap, size),
        None
    )
Transformation for Sequence.grouped
    :param wrap: wrap children values with this
    :param size: size of groups
    :return: transformation