def update_variant(self, variant_obj):
        """Update one variant document in the database.

        This means that the variant in the database will be replaced by variant_obj.

        Args:
            variant_obj(dict)

        Returns:
            new_variant(dict)
        """
        LOG.debug('Updating variant %s', variant_obj.get('simple_id'))

        new_variant = self.variant_collection.find_one_and_replace(
            {'_id': variant_obj['_id']},
            variant_obj,
            return_document=pymongo.ReturnDocument.AFTER
        )
        return new_variant
Update one variant document in the database.

        This means that the variant in the database will be replaced by variant_obj.

        Args:
            variant_obj(dict)

        Returns:
            new_variant(dict)