def group(face_ids, custom_headers:nil)
      response = group_async(face_ids, custom_headers:custom_headers).value!
      response.body unless response.nil?
    end
def group(face_ids, custom_headers:nil)
      response = group_async(face_ids, custom_headers:custom_headers).value!
      response.body unless response.nil?
    end
Divide candidate faces into groups based on face similarity.<br />
 * 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 [Face -
 Verify](/docs/services/563879b61984550e40cbbe8d/operations/563879b61984550f3039523a)
 when you only have 2 candidate faces.
 * The 'recognitionModel' associated with the query faces' faceIds should be
 the same.


 @param face_ids Array of candidate faceId created by Face - Detect. The
 maximum is 1000 faces
 @param custom_headers [Hash{String => String}] A hash of custom headers that
 will be added to the HTTP request.

 @return [GroupResult] operation results.