What is the specific definition of a 'Guru's biography' as outlined in the source text?

A Guru's biography is defined as a 'reliable and true book' dedicated to chronicling the master's life. According to the details provided in Chapter 0, such a text should describe the Guru's incarnation, their journey through childhood, youth, and old age, their wonderful plays or 'Leelas', their incomparable miracles, and the significant works accomplished during their incarnation. This specific focus on the life and divine activities of the Guru is what distinguishes these biographies from other types of spiritual knowledge texts mentioned in the preface.