code: public static MutableDoubleTuple normalize(
          DoubleTuple t, MutableDoubleTuple result)
      {
          result = validate(t, result);
          double inv = 1.0 / computeL2(t);
          return DoubleTupleFunctions.apply(
              t, (a)->(a * inv), result);
      }
docs: Normalize the given tuple and write the result into
  the given result tuple. That is, the given tuple
  is divided by its {@link #computeL2(DoubleTuple) L2 norm}.
  
  @param t The input tuple
  @param result The tuple that will store the result
  @return The result tuple
  @throws IllegalArgumentException If the given tuples do not
  have the same {@link Tuple#getSize() size}