code: def crypto_sign_keypair():
      
      pk = ffi.new("unsigned char[]", crypto_sign_PUBLICKEYBYTES)
      sk = ffi.new("unsigned char[]", crypto_sign_SECRETKEYBYTES)
  
      rc = lib.crypto_sign_keypair(pk, sk)
      ensure(rc == 0,
             'Unexpected library error',
             raising=exc.RuntimeError)
  
      return (
          ffi.buffer(pk, crypto_sign_PUBLICKEYBYTES)[:],
          ffi.buffer(sk, crypto_sign_SECRETKEYBYTES)[:],
      )
docs: Returns a randomly generated public key and secret key.
  
      :rtype: (bytes(public_key), bytes(secret_key))