<dd><code>matches</code> - Matches. If a query descriptor is masked out in mask , no match is added for this
     descriptor. So, matches size may be smaller than the query descriptors count.</dd>
<dd><code>mask</code> - Mask specifying permissible matches between an input query and train matrices of
     descriptors.

     In the first variant of this method, the train descriptors are passed as an input argument. In the
     second variant of the method, train descriptors collection that was set by Descrip