RSVP parameter leads to error.

[Noord]

Valid calendar definition with rsvp param.

BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//SmartCal//prodid//EN
METHOD:REQUEST
DTEND:20240112T130000Z
DTSTART:20240112T120000Z
SUMMARY:summary1
BEGIN:VEVENT
SUMMARY:summary2
DTSTART:20240112T120000Z
DTEND:20240112T130000Z
DTSTAMP:20240108T160153Z
UID:1704729713/asdf@redacted.org
ATTENDEE;CN="abc";CUTYPE=INDIVIDUAL;PARTSTAT=NEEDS-ACTION;ROLE=REQ-PARTIC
  IPANT;RSVP=TRUE:MAILTO:participant1@redacted.org
ATTENDEE;CN="def";CUTYPE=INDIVIDUAL;PARTSTAT=NEEDS-ACTION;ROLE=REQ-PARTIC
  IPANT;RSVP=TRUE:MAILTO:participant2@redacted.org
LOCATION:Office
ORGANIZER;CN="hij";ROLE=NON-PARTICIPANT:MAILTO:organizer@redacted.org
PRIORITY:5
STATUS:CONFIRMED
END:VEVENT
END:VCALENDAR

Read, parse and serialize again.

import ics

content = open("/tmp/invite.ics", "r").read()
cal = ics.Calendar(content) # able to parse it

filename_event = '/tmp/invite-new.ics'
with open(filename_event, 'w') as ics_file:
    ics_file.writelines(cal)

boom.

Traceback (most recent call last):
  File "~/test.py", line 9, in <module>
    ics_file.writelines(cal)
  File "~/python3.10/site-packages/ics/icalendar.py", line 107, in __iter__
    yield from self.serialize_iter()
  File "~/python3.10/site-packages/ics/component.py", line 81, in serialize_iter
    return self.serialize().splitlines(keepends=True)
  File "~/python3.10/site-packages/ics/component.py", line 72, in serialize
    output(self, container)
  File "~/python3.10/site-packages/ics/serializers/icalendar_serializer.py", line 27, in serialize_event
    container.append(event.serialize())
  File "~/python3.10/site-packages/ics/component.py", line 73, in serialize
    return str(container)
  File "~/python3.10/site-packages/ics/grammar/parse.py", line 119, in __str__
    ret.append(str(line))
  File "~/python3.10/site-packages/ics/grammar/parse.py", line 59, in __str__
    params_str += ';{}={}'.format(pname, ','.join(self.params[pname]))
TypeError: sequence item 0: expected str instance, bool found