Write values to the targeted documents
        Values need to be a dict as : {document_id: value}

def write(self, values):
        """
        Write values to the targeted documents
        Values need to be a dict as : {document_id: value}
        """
        # Insert only for docs targeted by the target
        filtered = {_id: value for _id, value in values.items() if _id in self._document_ids}

        if not filtered:
            return

        bulk = self.get_collection().initialize_ordered_bulk_op()
        for _id, value in filtered.items():
            bulk.find({'_id': _id}).upsert() \
                    .update_one({'$set': {self._field: value}})

        bulk.execute()