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.

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