docs: public static LabeledPoint pointOf(Collection<Writable> writables) {
          double[] ret = new double[writables.size() - 1];
          int count = 0;
          double target = 0;
          for (Writable w : writables) {
              if (count < writables.size() - 1)
                  ret[count++] = Float.parseFloat(w.toString());
              else
                  target = Float.parseFloat(w.toString());
          }
  
          if (target < 0)
              throw new IllegalStateException("Target must be >= 0");
          return new LabeledPoint(target, Vectors.dense(ret));
      }