This is baked into the product. As there are many, many different ways that log files can be formatted, great care is taken to make sure many different log formats can be detected correctly. If you have a format that you think should be recognized but isn't, I would open a ticket with support.
Adam, when you say "log format" why do you exactly mean ? Byte-format (e.g. text vs binary), log entry format (e.g. single-line vs json vs xml), timestamp format or organization of the fields in the single log entry ?