def check_thresholds(self, service=None, use_ta=True):
        """
        Check all limits and current usage against their specified thresholds;
        return all :py:class:`~.AwsLimit` instances that have crossed
        one or more of their thresholds.

        If ``service`` is specified, the returned dict has one element,
        the service name, whose value is a nested dict as described below;
        otherwise it includes all known services.

        The returned :py:class:`~.AwsLimit` objects can be interrogated
        for their limits (:py:meth:`~.AwsLimit.get_limit`) as well as
        the details of usage that crossed the thresholds
        (:py:meth:`~.AwsLimit.get_warnings` and
        :py:meth:`~.AwsLimit.get_criticals`).

        See :py:meth:`.AwsLimit.check_thresholds`.

        :param service: the name(s) of one or more service(s) to return
          results for
        :type service: list
        :param use_ta: check Trusted Advisor for information on limits
        :type use_ta: bool
        :returns: dict of service name (string) to nested dict
          of limit name (string) to limit (:py:class:`~.AwsLimit`)
        :rtype: dict
        """
        res = {}
        to_get = self.services
        if service is not None:
            to_get = dict((each, self.services[each]) for each in service)
        if use_ta:
            self.ta.update_limits()
        for sname, cls in to_get.items():
            if hasattr(cls, '_update_limits_from_api'):
                cls._update_limits_from_api()
            tmp = cls.check_thresholds()
            if len(tmp) > 0:
                res[sname] = tmp
        return res
Check all limits and current usage against their specified thresholds;
        return all :py:class:`~.AwsLimit` instances that have crossed
        one or more of their thresholds.

        If ``service`` is specified, the returned dict has one element,
        the service name, whose value is a nested dict as described below;
        otherwise it includes all known services.

        The returned :py:class:`~.AwsLimit` objects can be interrogated
        for their limits (:py:meth:`~.AwsLimit.get_limit`) as well as
        the details of usage that crossed the thresholds
        (:py:meth:`~.AwsLimit.get_warnings` and
        :py:meth:`~.AwsLimit.get_criticals`).

        See :py:meth:`.AwsLimit.check_thresholds`.

        :param service: the name(s) of one or more service(s) to return
          results for
        :type service: list
        :param use_ta: check Trusted Advisor for information on limits
        :type use_ta: bool
        :returns: dict of service name (string) to nested dict
          of limit name (string) to limit (:py:class:`~.AwsLimit`)
        :rtype: dict