code: public static DoubleBinding sqrt(final ObservableDoubleValue a) {
          return createDoubleBinding(() -> Math.sqrt(a.get()), a);
      }
docs: Binding for {@link java.lang.Math#sqrt(double)}
  
  @param   a   a value.
  @return  the positive square root of {@code a}.
  If the argument is NaN or less than zero, the result is NaN.