Is Li Shutong's farewell a poem or a song? If it is a poem, what is the epigraph?

As far as I know, there are three kinds of statements. The first is that there is no epigraph, and the second is that the epigraph is Xi Qian Ying, but the original saying "semi-scattered bosom friend" should be six words, which is the master's flexible use here. The third is that Ruan Langgui is a double tone with four rhymes on the top and four rhymes on the bottom. Four sentences in the upper part and five sentences in the lower part. Farewell is taken from the sentence pattern under Ruan Langgui's epitaph, and the rhyme has been changed.