code: def _match_metric(self, metric):
          
          if len(self._compiled_filters) == 0:
              return True
          for (collector, filter_regex) in self._compiled_filters:
              if collector != metric.getCollectorPath():
                  continue
              if filter_regex.match(metric.getMetricPath()):
                  return True
          return False
docs: matches the metric path, if the metrics are empty, it shorts to True