def _read_last_lines(num_lines, mesos_file):
    file_size = mesos_file.size()

    # estimate how much data we need to fetch to read `num_lines`.
    fetch_size = LINE_SIZE * num_lines

    end = file_size
    start = max(end - fetch_size, 0)
    data = ''
    while True:
        # fetch data
        mesos_file.seek(start)
        data = mesos_file.read(end - start) + data

        # break if we have enough lines
        data_tmp = _strip_trailing_newline(data)
        lines = data_tmp.split('\n')
        if len(lines) > num_lines:
            ret = lines[-num_lines:]
            break
        elif start == 0:
            ret = lines
            break

        # otherwise shift our read window and repeat
        end = start
        start = max(end - fetch_size, 0)

    mesos_file.seek(file_size)
    return ret
Returns the last `num_lines` of a file, or less if the file is
dataset/ETHPy150Open shopkeep/shpkpr/shpkpr/files.py/_read_last_lines