The collection of session entities overrides the collection of entities
in the corresponding custom entity type.
Supplement
The collection of session entities extends the collection of entities in
the corresponding custom entity type.
Note: Even in this override mode calls to ListSessionEntityTypes,
GetSessionEntityType, CreateSessionEntityType and
UpdateSessionEntityType only return the additional entities added in
this session entity type. If you want to get the supplemented list,
please call
[EntityTypes.GetEntityType][google.cloud.dialogflow.cx.v3.EntityTypes.GetEntityType]
on the custom entity type and merge.
