code: def verticalLine(requestContext, ts, label=None, color=None):
      
      ts = int(epoch(parseATTime(ts, requestContext['tzinfo'])))
      start = int(epoch(requestContext['startTime']))
      end = int(epoch(requestContext['endTime']))
      if ts < start:
          raise ValueError("verticalLine(): timestamp %s exists "
                           "before start of range" % ts)
      elif ts > end:
          raise ValueError("verticalLine(): timestamp %s exists "
                           "after end of range" % ts)
      start = end = ts
      step = 1.0
      series = TimeSeries(label, start, end, step, [1.0, 1.0])
      series.options['drawAsInfinite'] = True
      if color:
          series.color = color
      return [series]
docs: Takes a timestamp string ts.
  
      Draws a vertical line at the designated timestamp with optional
      'label' and 'color'. Supported timestamp formats include both
      relative (e.g. -3h) and absolute (e.g. 16:00_20110501) strings,
      such as those used with ``from`` and ``until`` parameters. When
      set, the 'label' will appear in the graph legend.
  
      Note: Any timestamps defined outside the requested range will
      raise a 'ValueError' exception.
  
      Example::
  
          &target=verticalLine("12:3420131108","event","blue")
          &target=verticalLine("16:00_20110501","event")
          &target=verticalLine("-5mins")