docs: @SuppressWarnings("unchecked")
      public <R> Value<R> map(Function<? super V, ? extends R> mapper) {
  
          LettuceAssert.notNull(mapper, "Mapper function must not be null");
  
          if (hasValue()) {
              return new Value<R>(mapper.apply(getValue()));
          }
  
          return (Value<R>) this;
      }