import math


def _IsInvalidWindow(latency_value):
  """Readability hepler for finding windows which delay cannot be determined.

  Args:
    latency_value: (tuple (float, float)) containing a timestamp and a delay
      value. Unit is seconds.

  Returns:
    True, if the corresponding window is invalid, False else.
  """
  return math.isnan(latency_value[1])