code: def balance_of(self, b58_address: str) -> int:
          
          func = InvokeFunction('balanceOf')
          Oep4.__b58_address_check(b58_address)
          address = Address.b58decode(b58_address).to_bytes()
          func.set_params_value(address)
          result = self.__sdk.get_network().send_neo_vm_transaction_pre_exec(self.__hex_contract_address, None, func)
          try:
              balance = ContractDataParser.to_int(result['Result'])
          except SDKException:
              balance = 0
          return balance
docs: This interface is used to call the BalanceOf method in ope4
          that query the ope4 token balance of the given base58 encode address.
  
          :param b58_address: the base58 encode address.
          :return: the oep4 token balance of the base58 encode address.