code: def add_metric(self, labels, value, created=None, timestamp=None):
          
          self.samples.append(Sample(self.name + '_total', dict(zip(self._labelnames, labels)), value, timestamp))
          if created is not None:
              self.samples.append(Sample(self.name + '_created', dict(zip(self._labelnames, labels)), created, timestamp))
docs: Add a metric to the metric family.
  
          Args:
            labels: A list of label values
            value: The value of the metric
            created: Optional unix timestamp the child was created at.