public InMemorySystemDescriptor withInMemoryScope(String inMemoryScope) {
    this.inMemoryScope = inMemoryScope;
    return this;
  }
{@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