def TimelineName(name, source_type, value_type):
  """Constructs the standard name given in the timeline.

  Args:
    name: The name of the timeline, for example "total", or "render_compositor".
    source_type: One of "cpu", "gpu" or None. None is only used for total times.
    value_type: the type of value. For example "mean", "stddev"...etc.
  """
  if source_type:
    return '%s_%s_%s_time' % (name, value_type, source_type)
  else:
    return '%s_%s_time' % (name, value_type)