<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def add_journal(self, units=None, boot=None, since=None, until=None, lines=None, allfields=False, output=None, timeout=None, identifier=None, catalog=None, sizelimit=None, pred=None):
 """Collect journald logs from one of more units. :param units: A string, or list of strings specifying the systemd units for which journal entries will be collected. :param boot: A string selecting a boot index using the journalctl syntax. The special values 'this' and 'last' are also accepted. :param since: A string representation of the start time for journal messages. :param until: A string representation of the end time for journal messages. :param lines: The maximum number of lines to be collected. :param allfields: A bool. Include all journal fields regardless of size or non-printable characters. :param output: A journalctl output control string, for example "verbose". :param timeout: An optional timeout in seconds. :param identifier: An optional message identifier. :param catalog: Bool. If True, augment lines with descriptions from the system catalog. :param sizelimit: Limit to the size of output returned in MB. Defaults to the value of --log-size. """

        journal_cmd = "journalctl --no-pager "
        unit_opt = " --unit %s"
        boot_opt = " --boot %s"
        since_opt = " --since %s"
        until_opt = " --until %s"
        lines_opt = " --lines %s"
        output_opt = " --output %s"
        identifier_opt = " --identifier %s"
        catalog_opt = " --catalog"

        journal_size = 100
        all_logs = self.get_option("all_logs")
        log_size = sizelimit or self.get_option("log_size")
        log_size = max(log_size, journal_size) if not all_logs else 0

        if isinstance(units, six.string_types):
            units = [units]

        if units:
            for unit in units:
                journal_cmd += unit_opt % unit

        if identifier:
            journal_cmd += identifier_opt % identifier

        if catalog:
            journal_cmd += catalog_opt

        if allfields:
            journal_cmd += " --all"

        if boot:
            if boot == "this":
                boot = ""
            if boot == "last":
                boot = "-1"
            journal_cmd += boot_opt % boot

        if since:
            journal_cmd += since_opt % since

        if until:
            journal_cmd += until_opt % until

        if lines:
            journal_cmd += lines_opt % lines

        if output:
            journal_cmd += output_opt % output

        self._log_debug("collecting journal: %s" % journal_cmd)
        self._add_cmd_output(journal_cmd, timeout=timeout,
                             sizelimit=log_size, pred=pred)