@classmethod<EOL><INDENT>def pre_filter(self, queryset, user):<DEDENT>
<EOL>queryset = queryset.filter(<EOL>proposal_kind__proposalbase__presentation__cancelled=False<EOL>)<EOL>u = user<EOL>user_is_presenter = Q(<EOL>is_presenter=True,<EOL>proposal_kind__proposalbase__presentation__speaker__user=u,<EOL>)<EOL>user_is_copresenter = Q(<EOL>is_copresenter=True,<EOL>proposal_kind__proposalbase__presentation__additional_speakers__user=u,  <EOL>)<EOL>return queryset.filter(user_is_presenter | user_is_copresenter)<EOL>
Returns all of the items from queryset which are enabled by a user
        being a presenter or copresenter of a non-cancelled proposal.