@NonNull Executor executor() {
        return this.executor;
    }
Get a collection of all the {@link TypeToken} of all implementations for a given type.

@param type      The {@link TypeToken} of the service to get implementations for.
@param <Context> The context type.
@param <Result>  The result type.
@param <S>       The service type.
@return Returns an collection of the {@link TypeToken}s of the implementations for a given
        service. Iterator order matches the priority when pumping contexts through the pipeline
cloud-services/src/main/java/org/incendo/cloud/services/ServicePipeline.java