@Override
  public Map<String, String> toConfig() {
    HashMap<String, String> configs = new HashMap<>(super.toConfig());
    configs.put(InMemorySystemConfig.INMEMORY_SCOPE, this.inMemoryScope);
    configs.put(String.format(SystemConfig.SYSTEM_FACTORY_FORMAT, getSystemName()), FACTORY_CLASS_NAME);
    return configs;
  }
{@code inMemoryScope} defines the unique instance of InMemorySystem, that this system uses
This method is framework use only, users are not supposed to use it

@param inMemoryScope acts as a unique global identifier for this instance of InMemorySystem
@return this system descriptor
samza-test/src/main/java/org/apache/samza/test/framework/system/descriptors/InMemorySystemDescriptor.java