def METHOD_NAME(x):
    r"""
    Return True if x is the modular group `\SL_2(\ZZ)`.
    EXAMPLES::
        sage: from sage.modular.arithgroup.all import is_SL2Z
        sage: is_SL2Z(SL2Z)
        True
        sage: is_SL2Z(Gamma0(6))
        False
    """
    return isinstance(x, SL2Z_class)