The output is one or more disjointed face groups and a messyGroup. A face group contains faces that have similar looking, often of the same person. Face groups are ranked by group size, i.e. number of faces. Notice that faces belonging to a same person might be split into several groups in the result.
MessyGroup is a special face group containing faces that cannot find any similar counterpart face from original faces. The messyGroup will not appear in the result if all faces found their counterparts.
Group API needs at least 2 candidate faces and 1000 at most. We suggest to try "Verify Face To Face" when you only have 2 candidate faces.
The 'recognitionModel' associated with the query faces' faceIds should be the same.