code: def Sign(verifiable, keypair):
          
          prikey = bytes(keypair.PrivateKey)
          hashdata = verifiable.GetHashData()
          res = Crypto.Default().Sign(hashdata, prikey)
          return res
docs: Sign the `verifiable` object with the private key from `keypair`.
  
          Args:
              verifiable:
              keypair (neocore.KeyPair):
  
          Returns:
              bool: True if successfully signed. False otherwise.