In addition to the DB datastore exceptions, the NDB datastore provides the following exception classes:
- exception ComputedPropertyError()
- Raised when attempting to set a value to or delete a computed property.
- exception InvalidPropertyError()
- Raised when a property is not applicable to a given use. For example, a property must exist and be indexed to be used in a query's projection or group by clause.
- exception ReadonlyPropertyError()
- Raised when attempting to set a property value that is read-only.
- exception UnprojectedPropertyError()
- Raised when getting a property value that's not in the projection.
