What evidence does the author provide to support the claim that the tradition of writing a Guru's biography is an ancient practice?

The text asserts that the practice of writing a Guru's biography is very ancient and provides specific scriptural evidence to substantiate this claim. According to Chapter 0, the tradition is mentioned in the Narada Purana. The author states, "The service of writing a Guru's biography is mentioned in the Narada Purana; thus, there is no doubt it is very ancient." This reference to a well-known and ancient Purana is used to establish the historical lineage and deep-rooted origin of this form of Guru service, confirming it is not a modern convention but a time-honored spiritual practice.