code: def identity(requestContext, name, step=60):
      
      start = int(epoch(requestContext["startTime"]))
      end = int(epoch(requestContext["endTime"]))
      values = range(start, end, step)
      series = TimeSeries(name, start, end, step, values)
      series.pathExpression = 'identity("%s")' % name
  
      return [series]
docs: Identity function:
      Returns datapoints where the value equals the timestamp of the datapoint.
      Useful when you have another series where the value is a timestamp, and
      you want to compare it to the time of the datapoint, to render an age
  
      Example::
  
          &target=identity("The.time.series")
  
      This would create a series named "The.time.series" that contains points
      where x(t) == t.
  
      Accepts optional second argument as 'step' parameter (default step is
      60 sec)