code: def get_default_account_data(self) -> AccountData:
          
          for acct in self.wallet_in_mem.accounts:
              if not isinstance(acct, AccountData):
                  raise SDKException(ErrorCode.other_error('Invalid account data in memory.'))
              if acct.is_default:
                  return acct
          raise SDKException(ErrorCode.get_default_account_err)
docs: This interface is used to get the default account in WalletManager.
  
          :return: an AccountData object that contain all the information of a default account.