How to sample bytes if not all bytes are scanned. Meaningful only
when used in conjunction with bytes_limit_per_file. If not
specified, scanning would start from the top.
Values:
SAMPLE_METHOD_UNSPECIFIED (0):
No description available.
TOP (1):
Scan from the top (default).
RANDOM_START (2):
For each file larger than bytes_limit_per_file, randomly
pick the offset to start scanning. The scanned bytes are
contiguous.