code: func Enclose(chainID string, payload payload.Payload) *Envelope {
  	body := NewTx(payload)
  	body.ChainID = chainID
  	return body.Enclose()
  }
docs: // Enclose a Payload in an Envelope so it is ready to be signed by first wrapping the Payload
  // as a Tx (including ChainID) and writing it to the Tx field of the Envelope