code: def passphrase_to_key(self, passphrase):
          '''convert a passphrase to a 32 byte key'''
          import hashlib
          h = hashlib.new('sha256')
          h.update(passphrase)
          return h.digest(f passphrase_to_key(self, passphrase):
          '''convert a passphrase to a 32 byte key'''
          import hashlib
          h = hashlib.new('sha256')
          h.update(passphrase)
          return h.digest()
docs: convert a passphrase to a 32 byte key