generate questions: According to Mahayana tradition, the Mahayana sutras were transmitted in secret, came from other Buddhas or Bodhisattvas, or were preserved in non-human worlds because human beings at the time could not understand them:
What sutras were transmitted in secret? {sep_token} What sutras could have been preserved in non-human worlds? {sep_token} What tradition says that sutras might have come from other Buddhas or Bodhisattvas? {sep_token}