docs: def personal_sign(self, message, account, password=None):
          """https://github.com/ethereum/go-ethereum/wiki/Management-APIs#personal_sign
  
          :param message: Message for sign
          :type message: str
  
          :param account: Account address
          :type account: str
  
          :param password: Password of account (optional)
          :type password: str
  
          :return: signature
          :rtype: str
          """
          return (yield from self.rpc_call('personal_sign',
                                           [message, account, password]))