Performs validation
        :param obj_to_validate:
        :param is_substitute:
        :return: list of validation messages or None

def validate(self, obj_to_validate, is_substitute=True):
        """
        Performs validation
        :param obj_to_validate:
        :param is_substitute:
        :return: list of validation messages or None
        """
        res = []
        for check in self.__cfg[Validator.__CFG_KEY_CHECKS]:
            self.__logger.info('Performing {} validation against {}'.format(check, obj_to_validate))
            check_res = Check(self.__cfg[Validator.__CFG_KEY_CHECKS][check]).validate(obj_to_validate, is_substitute)
            if check_res:
                if type(check_res) == dict:
                    res.append(check_res)
                else:
                    res.extend(check_res)
        return None if len(res) == 0 else res