<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_output_content(job_id, max_size=1024, conn=None):
 """ returns the content buffer for a job_id if that job output exists :param job_id: <str> id for the job :param max_size: <int> truncate after [max_size] bytes :param conn: (optional)<connection> to run on :return: <str> or <bytes> """

    content = None
    if RBO.index_list().contains(IDX_OUTPUT_JOB_ID).run(conn):
        # NEW
        check_status = RBO.get_all(job_id, index=IDX_OUTPUT_JOB_ID).run(conn)
    else:
        # OLD
        check_status = RBO.filter({OUTPUTJOB_FIELD: {ID_FIELD: job_id}}).run(conn)
    for status_item in check_status:
        content = _truncate_output_content_if_required(status_item, max_size)
    return content