'Get real root isolating intervals for a square-free factor.'

@classmethod
def _get_reals_sqf(cls, factor):

    if (factor in _reals_cache):
        real_part = _reals_cache[factor]
    else:
        _reals_cache[factor] = real_part = dup_isolate_real_roots_sqf(factor.rep.rep, factor.rep.dom, blackbox=True)
    return real_part
