def add_attendees(self, attendees, required=True):
new_attendees = self._build_resource_dictionary(attendees, required=required)<EOL>for email in new_attendees:<EOL><INDENT>self._attendees[email] = new_attendees[email]<EOL><DEDENT>self._dirty_attributes.add(u'<STR_LIT>')<EOL>
Adds new attendees to the event.

*attendees* can be a list of email addresses or :class:`ExchangeEventAttendee` objects.