docs: def pexpireat(self, name, when):
          """
          Set an expire flag on key ``name``. ``when`` can be represented
          as an integer representing unix time in milliseconds (unix time * 1000)
          or a Python datetime object.
          """
          if isinstance(when, datetime.datetime):
              ms = int(when.microsecond / 1000)
              when = int(mod_time.mktime(when.timetuple())) * 1000 + ms
          return self.execute_command('PEXPIREAT', name, when)