docs: def FormatTime(fmt, stime = None):
    """A compatibility wrapper for the `strftime` function.
  
    It is guaranteed to always take unicode string as an argument and return an
    unicode string as a result.
  
    Args:
      fmt: A format string specifying formatting of the output.
      stime: A time representation as returned by `gmtime` or `localtime`.
  
    Returns:
      A human-readable representation of `stime`.
    """
    precondition.AssertType(fmt, str)
    precondition.AssertOptionalType(stime, time.struct_time)
  
    # TODO(hanuszczak): https://github.com/google/pytype/issues/127
    # pytype: disable=wrong-arg-types
    # We need this because second parameter is not a keyword argument, so method
    # must be explicitly called with or without it.
    if stime is None:
      strftime = time.strftime
    else:
      strftime = lambda fmt: time.strftime(fmt, stime)
  
    if PY2:
      return strftime(fmt.encode("ascii")).decode("ascii")
    else:
      return strftime(fmt)