public Optional<ApplicationContainerContextFactory<ApplicationContainerContext>> getApplicationContainerContextFactory() {
    @SuppressWarnings("unchecked") // ok because all context types are at least ApplicationContainerContext
    Optional<ApplicationContainerContextFactory<ApplicationContainerContext>> factoryOptional =
        (Optional) this.applicationContainerContextFactoryOptional;
    return factoryOptional;
  }
Get the {@link ApplicationContainerContextFactory} specified by the application.

@return {@link ApplicationContainerContextFactory} if application specified it; empty otherwise
samza-core/src/main/java/org/apache/samza/application/descriptors/ApplicationDescriptorImpl.java