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

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

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

        :return: Job definition or None
        :rtype: JobDefinition or None
        """
        env = self.get_job_definition_by_arn(identifier)
        if env is None:
            env = self.get_job_definition_by_name(identifier)
        return env