docs: def create_metric_definition(self, metric_type, metric_id, **tags):
          """
          Create metric definition with custom definition. **tags should be a set of tags, such as
          units, env ..
  
          :param metric_type: MetricType of the new definition
          :param metric_id: metric_id is the string index of the created metric
          :param tags: Key/Value tag values of the new metric
          """
          item = { 'id': metric_id }
          if len(tags) > 0:
              # We have some arguments to pass..
              data_retention = tags.pop('dataRetention', None)
              if data_retention is not None:
                  item['dataRetention'] = data_retention
  
              if len(tags) > 0:
                  item['tags'] = tags
  
          json_data = json.dumps(item, indent=2)
          try:
              self._post(self._get_url(metric_type), json_data)
          except HawkularError as e:
              if e.code == 409:
                  return False
              raise e
  
          return True