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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _fetch_contribution_info(self):
 """Build the list of information entries for contributions of the event"""

        self.contributions = {}
        query = (Contribution.query
                 .with_parent(self.event)
                 .options(joinedload('legacy_mapping'),
                          joinedload('timetable_entry').lazyload('*')))
        for contribution in query:
            if not contribution.start_dt:
                continue
            cid = (contribution.legacy_mapping.legacy_contribution_id if contribution.legacy_mapping
                   else contribution.id)
            key = '{}t{}'.format(contribution.event_id, cid)
            self.contributions[key] = u'{} ({})'.format(contribution.title,
                                                        to_unicode(format_time(contribution.start_dt)))