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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 _get_collection_for_user(self, collection_id, user):
 """Check that collection exists and user has `add` permission."""

        collection_query = Collection.objects.filter(pk=collection_id)
        if not collection_query.exists():
            raise exceptions.ValidationError('Collection id does not exist')

        collection = collection_query.first()
        if not user.has_perm('add_collection', obj=collection):
            if user.is_authenticated:
                raise exceptions.PermissionDenied()
            else:
                raise exceptions.NotFound()

        return collection