Possible to provide an escape hatch for expressions?

[max-sixty]

Firstly thanks for the awesome library. We use it in https://github.com/prql/prql to format SQL once our compiler has produced it, from sqlparser-rs.

A couple of times we've wanted to not format an expression, maybe because it's not standard SQL. Here's an example that just came up: https://github.com/prql/prql/issues/965

Do you have any thoughts for how best to manage that? We could use a sentinel and then replace it afterwards? Or would this library be open to something like a <ignore> tag / -- format-ignore comment?