code: public static double harmonicMean(DoubleTuple t)
      {
          double s =
              DoubleTupleFunctions.reduce(t, 0.0, (a, b) -> (a + (1.0 / b)));
          return t.getSize() / s;
      }
docs: Returns the harmonic mean of the given tuple
  
  @param t The input tuple
  @return The mean