<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_available_ip4(self, id_network):
 """ Get a available IP in the network ipv4 :param id_network: Network identifier. Integer value and greater than zero. :return: Dictionary with the following structure: :: {'ip': {'ip': < available_ip >}} :raise IpNotAvailableError: Network dont have available IP for insert a new IP :raise NetworkIPv4NotFoundError: Network is not found :raise UserNotAuthorizedError: User dont have permission to get a available IP :raise InvalidParameterError: Network identifier is null or invalid. :raise XMLError: Networkapi failed to generate the XML response. :raise DataBaseError: Networkapi failed to access the database. """


        if not is_valid_int_param(id_network):
            raise InvalidParameterError(
                u'Network identifier is invalid or was not informed.')

        url = 'ip/availableip4/' + str(id_network) + "/"

        code, xml = self.submit(None, 'GET', url)

        return self.response(code, xml)