code: def add_account(self, accounts):
          
          with self.unlock_cond:
              for account in to_list(accounts):
                  account.acquired_event.listen(self._on_account_acquired)
                  account.released_event.listen(self._on_account_released)
                  self.accounts.add(account)
                  self.unlocked_accounts.append(account)
              self.unlock_cond.notify_all()
docs: Adds one or more account instances to the pool.
  
          :type  accounts: Account|list[Account]
          :param accounts: The account to be added.