code: @Override
      public Metric[] compareBulk(CompareModels... compareModels) throws JsonProcessingException, ApiException {
          if (LOG.isDebugEnabled()) {
              LOG.debug("Compare " + compareModels.length + " pairs.");
          }
          if (compareModels == null || compareModels.length == 0) {
              throw new IllegalArgumentException(NULL_MODEL_MSG);
          }
          Model[][] toCompare = new Model[compareModels.length][2];
          int i = 0;
          for (CompareModels pair: compareModels) {
              toCompare[i++] = pair.getModels();
          }
          return compareApi.compareBulk(toJsonBulk(toCompare), this.retinaName);
      }
docs: {@inheritDoc}