def METHOD_NAME(self, req_authn_context=None):
    """
    Given the authentication context find zero or more places where
    the user could be sent next. Ordered according to security level.
    :param req_authn_context: The requested context as an
        RequestedAuthnContext instance
    :return: An URL
    """
    if req_authn_context is None:
        return self._pick_by_class_ref(UNSPECIFIED, "minimum")
    if req_authn_context.authn_context_class_ref:
        if req_authn_context.comparison:
            _cmp = req_authn_context.comparison
        else:
            _cmp = "exact"
        if _cmp == "exact":
            res = []
            for cls_ref in req_authn_context.authn_context_class_ref:
                res += self._pick_by_class_ref(cls_ref.text, _cmp)
            return res
        else:
            return self._pick_by_class_ref(req_authn_context.authn_context_class_ref[0].text, _cmp)
    elif req_authn_context.authn_context_decl_ref:
        if req_authn_context.comparison:
            _cmp = req_authn_context.comparison
        else:
            _cmp = "exact"
        return self._pick_by_class_ref(req_authn_context.authn_context_decl_ref, _cmp)