code: public List<SimilarFace> findSimilar(UUID faceId, FindSimilarOptionalParameter findSimilarOptionalParameter) {
          return findSimilarWithServiceResponseAsync(faceId, findSimilarOptionalParameter).toBlocking().single().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
  @throws APIErrorException thrown if the request is rejected by server
  @throws RuntimeException all other wrapped checked exceptions if the request fails to be sent
  @return the List&lt;SimilarFace&gt; object if successful.