docs: def timestamp_to_str(t, datetime_format=DATETIME_FORMAT, *, inverse=False):
      """
      Given a POSIX timestamp (integer) ``t``,
      format it as a datetime string in the given format.
      If ``inverse``, then do the inverse, that is, assume ``t`` is
      a datetime string in the given format and return its corresponding
      timestamp.
      If ``format is None``, then return ``t`` as a string
      (if not ``inverse``) or as an integer (if ``inverse``) directly.
      """
      if not inverse:
          if datetime_format is None:
              result = str(t)
          else:
              result = dt.datetime.fromtimestamp(t).strftime(datetime_format)
      else:
          if format is None:
              result = int(t)
          else:
              result = dt.datetime.strptime(t, datetime_format).timestamp()
      return result