AutoValue instances should be deeply immutable. Therefore, we recommend using immutable types for fields. E.g., use ImmutableMap instead of Map, ImmutableSet instead of Set, etc.

Read more at https://github.com/google/auto/blob/master/value/userguide/builders-howto.md#-use-a-collection-valued-property

Suppress violations by using @SuppressWarnings("AutoValueImmutableFields") on the relevant abstract getter.