docs: public KeyedStream<T, Tuple> keyBy(int... fields) {
  		if (getType() instanceof BasicArrayTypeInfo || getType() instanceof PrimitiveArrayTypeInfo) {
  			return keyBy(KeySelectorUtil.getSelectorForArray(fields, getType()));
  		} else {
  			return keyBy(new Keys.ExpressionKeys<>(fields, getType()));
  		}
  	}