def METHOD_NAME():
    """
    Return SL2Z. (Used for pickling SL2Z.)
    EXAMPLES::
        sage: sage.modular.arithgroup.congroup_sl2z._SL2Z_ref()
        Modular Group SL(2,Z)
        sage: sage.modular.arithgroup.congroup_sl2z._SL2Z_ref() is SL2Z
        True
    """
    return SL2Z