code: def _create_propose_txn(signer, setting_key_value):
      
      setting_key, setting_value = setting_key_value
      nonce = hex(random.randint(0, 2**64))
      proposal = SettingProposal(
          setting=setting_key,
          value=setting_value,
          nonce=nonce)
      payload = SettingsPayload(data=proposal.SerializeToString(),
                                action=SettingsPayload.PROPOSE)
  
      return _make_txn(signer, setting_key, payload)
docs: Creates an individual sawtooth_settings transaction for the given
      key and value.