docs: private static double findPrototype(DistanceQuery<?> dq, DBIDs cx, DBIDs cy, DBIDVar prototype, double minMaxDist) {
      for(DBIDIter i = cx.iter(); i.valid(); i.advance()) {
        // Maximum distance of i to all elements in cy
        double maxDist = findMax(dq, i, cy, 0., minMaxDist);
        if(maxDist >= minMaxDist) {
          // We already have an at least equally good candidate.
          continue;
        }
        // Maximum distance of i to all elements in cx
        maxDist = findMax(dq, i, cx, maxDist, minMaxDist);
  
        // New best solution?
        if(maxDist < minMaxDist) {
          minMaxDist = maxDist;
          prototype.set(i);
        }
      }
      return minMaxDist;
    }