code: def Record(self, value, fields=None):
      
      key = _FieldsToKey(fields)
      metric_value = self._metric_values.get(key)
      if metric_value is None:
        metric_value = self._DefaultValue()
        self._metric_values[key] = metric_value
      metric_value.Record(value)
docs: Records the given observation in a distribution.