Return the stats object for a specific item=value in JSON format.

        Stats should be a list of dict (processlist, network...)

def get_stats_value(self, item, value):
        """Return the stats object for a specific item=value in JSON format.

        Stats should be a list of dict (processlist, network...)
        """
        if not isinstance(self.stats, list):
            return None
        else:
            if value.isdigit():
                value = int(value)
            try:
                return self._json_dumps({value: [i for i in self.stats if i[item] == value]})
            except (KeyError, ValueError) as e:
                logger.error(
                    "Cannot get item({})=value({}) ({})".format(item, value, e))
                return None