What is the function of quoting ancient poems in the fourth paragraph of lilac knot genealogy?

For many years, the author's heart has been filled with lilacs and poems about lilacs sung by the ancients. Suddenly, a bud with a handle like a knot was found in a spring rain, so it was associated with the poem "Lilacs are empty and sad in the rain" and the author's understanding of life began. Starting from the poem "Lilac Knot" written by the ancients, the author writes about the light rain, the troubles and disappointments of life, and the "knot" of life, otherwise it is a plain understanding of life, revealing the author's insight into the world and his free and easy life.