code: def get_allowance(self, asset_name: str, from_address: str, to_address: str, is_full: bool = False) -> str:
          
          payload = self.generate_json_rpc_payload(RpcMethod.GET_ALLOWANCE, [asset_name, from_address, to_address])
          response = self.__post(self.__url, payload)
          if is_full:
              return response
          return response['result']
docs: This interface is used to get the the allowance
          from transfer-from account to transfer-to account in current network.
  
          :param asset_name:
          :param from_address: a base58 encoded account address.
          :param to_address: a base58 encoded account address.
          :param is_full:
          :return: the information of allowance in dictionary form.