Literature review is usually written in the opening report or paper outline, so it doesn't matter whether it is written in the paper or not. The reason why you want to write a literature review is to let you know other people's research achievements and progress in this field, let you refer to other people's ideas, and let you know what are the shortcomings in this field, and then this is your research focus. To put it simply, it is to let you stand on the shoulders of "giants", learn research ideas by the way, and exercise your ability to summarize.