docs: def generate_key_pair(secret=None):
      """Generates a cryptographic key pair.
      Args:
          secret (:class:`string`): A secret that serves as a seed
      Returns:
          :class:`~bigchaindb.common.crypto.CryptoKeypair`: A
          :obj:`collections.namedtuple` with named fields
          :attr:`~bigchaindb.common.crypto.CryptoKeypair.private_key` and
          :attr:`~bigchaindb.common.crypto.CryptoKeypair.public_key`.
      """
      if secret:
          keypair_raw = ed25519_generate_key_pair_from_secret(secret)
          return CryptoKeypair(
              *(k.decode() for k in keypair_raw))
      else:
          return generate_keypair()