code: def for_account_hash(parent, account_hash):
          
          account = AccountProxy(parent)
          account.account_hash = account_hash
          if account.acquire():
              return account
          return None
docs: Returns a new AccountProxy that acquires the account with the
          given hash, if such an account is known to the account manager.
          It is an error if the account manager does not have such an
          account.