code: public Observable<HierarchicalChildEntity> getHierarchicalEntityChildAsync(UUID appId, String versionId, UUID hEntityId, UUID hChildId) {
          return getHierarchicalEntityChildWithServiceResponseAsync(appId, versionId, hEntityId, hChildId).map(new Func1<ServiceResponse<HierarchicalChildEntity>, HierarchicalChildEntity>() {
              @Override
              public HierarchicalChildEntity call(ServiceResponse<HierarchicalChildEntity> response) {
                  return response.body();
              }
          });
      }
docs: Gets information about the hierarchical entity child model.
  
  @param appId The application ID.
  @param versionId The version ID.
  @param hEntityId The hierarchical entity extractor ID.
  @param hChildId The hierarchical entity extractor child ID.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the HierarchicalChildEntity object