Who is the teacher talking about?

Yu Jiaxi. Teacher Yu Zi said that he was not Nanzhao, but one of the important figures in the literary history of the Tang Dynasty and was known as the first essayist in the Tang Dynasty. His style of writing is fresh and lively, graceful and smooth, full of lofty sentiments and spirituality of literati. His representative works, such as Notes on Nanzhao, Little Stone Pond and Poem on June 1st, became the classics of Tang literature.