Get job defintiion by name or ARN
        :param identifier: Name or ARN
        :type identifier: str

        :return: Job definition or None
        :rtype: list of JobDefinition

def get_job_definitions(self, identifier):
        """
        Get job defintiion by name or ARN
        :param identifier: Name or ARN
        :type identifier: str

        :return: Job definition or None
        :rtype: list of JobDefinition
        """
        result = []
        env = self.get_job_definition_by_arn(identifier)
        if env is not None:
            result.append(env)
        else:
            for value in self._job_definitions.values():
                if value.name == identifier:
                    result.append(value)

        return result