code: def _tag_from_regex(self, tags_regex, service_name):
          
          if not tags_regex or not service_name:
              return []
  
          match = re.compile(tags_regex).match(service_name)
  
          if not match:
              return []
  
          # match.groupdict() returns tags dictionary in the form of {'name': 'value'}
          # convert it to Datadog tag LIST: ['name:value']
          return ["%s:%s" % (name, value) for name, value in iteritems(match.groupdict())]
docs: Use a named regexp on the current service_name to create extra tags
          Example HAProxy service name: be_edge_http_sre-prod_elk
          Example named regexp: be_edge_http_(?P<team>[a-z]+)\\-(?P<env>[a-z]+)_(?P<app>.*)
          Resulting tags: ['team:sre','env:prod','app:elk']