code: public Observable<List<SimilarFace>> findSimilarAsync(UUID faceId, FindSimilarOptionalParameter findSimilarOptionalParameter) {
          return findSimilarWithServiceResponseAsync(faceId, findSimilarOptionalParameter).map(new Func1<ServiceResponse<List<SimilarFace>>, List<SimilarFace>>() {
              @Override
              public List<SimilarFace> call(ServiceResponse<List<SimilarFace>> response) {
                  return response.body();
              }
          });
      }
docs: Given query face's faceId, find the similar-looking faces from a faceId array or a faceListId.
  
  @param faceId FaceId of the query face. User needs to call Face - Detect first to get a valid faceId. Note that this faceId is not persisted and will expire 24 hours after the detection call
  @param findSimilarOptionalParameter the object representing the optional parameters to be set before calling this API
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the List&lt;SimilarFace&gt; object