Do not use 0.9. The original master README (now gone, but can be seen here rails-api/active_model_serializers · GitHub, read under Master - 0.9.0) for this version had the @options hash removed. The next release is supposed to bring that back.
@samnang you were correct with your response. However, context does not apply to the associations which is something I need.
@frank_west_iii I think this would explain why using active model serializers has been such a struggle so far. Following your advice has allowed me to use @options which solves my issues. Thanks!