What kind of literary thought does Du Fu's "Play as Six quatrains" show?

The play is six quatrains, which is a set of poems created by Du Fu, a great poet in the Tang Dynasty. This group of poems includes six seven-character quatrains. The first three poems are comments on the poet, and the last three poems are about the purpose of the poem. These six poems are independent poems in each capital, showing different themes. But at the same time, the spirits of these six poems are interrelated and an inseparable whole. This group of poems is essentially the summary of Du Fu's practical experience in poetry creation and the general outline of poetry theory. It involves a series of important theoretical issues related to the development of Tang poetry.