Mode: The type of commit to perform. Defaults to `TRANSACTIONAL`.
"MODE_UNSPECIFIED" - Unspecified. This value must not be used. "TRANSACTIONAL" - Transactional: The mutations are either all
applied, or none are applied. Learn about transactions [here](https://cloud.google.com/datastore/docs/concepts/transactions).
"NON_TRANSACTIONAL" - Non-transactional: The mutations may not
apply as all or none.