Induce a new subdivision--a lower level in the timing hierarchy.
    Subsequent calls to methods like stamp() operate on this new level.

    Notes:
        If rgstr_stamps is used, the collection is passed through set() for
        uniqueness, and the each entry is passed through str().  Any identifiers
        contained within are guaranteed to exist in the final dictionaries of
        stamp data when this timer closes. If any registered stamp was not
        actually encountered, zero values are populated.  (Can be useful if a
        subdivision is called repeatedly with conditional stamps.)

        The save_itrs input defaults to the current global default.  If save_itrs
        is True, then whenever another subdivision by the same name is added to
        the same position in the parent timer, and the two data structures are
        merged, any stamps present only as individual stamps (but not as itrs)
        will be made into itrs, with each subsequent data dump (when a subdivision
        is stopped) treated as another iteration.  (Consider multiple calls to a
        timer-wrapped subfunction within a loop.)  This setting does not
        affect any other timers in the hierarchy.

    Args:
        name (any): Identifer for the new timer, passed through str().
        rgstr_stamps (list,tuple, optional): Identifiers.
        save_itrs (bool, optional): Save individual iteration data.


    Returns:
        None

def subdivide(name, rgstr_stamps=None, save_itrs=SET['SI']):
    """
    Induce a new subdivision--a lower level in the timing hierarchy.
    Subsequent calls to methods like stamp() operate on this new level.

    Notes:
        If rgstr_stamps is used, the collection is passed through set() for
        uniqueness, and the each entry is passed through str().  Any identifiers
        contained within are guaranteed to exist in the final dictionaries of
        stamp data when this timer closes. If any registered stamp was not
        actually encountered, zero values are populated.  (Can be useful if a
        subdivision is called repeatedly with conditional stamps.)

        The save_itrs input defaults to the current global default.  If save_itrs
        is True, then whenever another subdivision by the same name is added to
        the same position in the parent timer, and the two data structures are
        merged, any stamps present only as individual stamps (but not as itrs)
        will be made into itrs, with each subsequent data dump (when a subdivision
        is stopped) treated as another iteration.  (Consider multiple calls to a
        timer-wrapped subfunction within a loop.)  This setting does not
        affect any other timers in the hierarchy.

    Args:
        name (any): Identifer for the new timer, passed through str().
        rgstr_stamps (list,tuple, optional): Identifiers.
        save_itrs (bool, optional): Save individual iteration data.


    Returns:
        None
    """
    _auto_subdivide(name, rgstr_stamps, save_itrs)
    f.t.is_user_subdvsn = True