- Remove `expect` in favor of `unwrap` when the `Result`'s error variant
contains the info in the `expect` anyway (eg. when locking things).
The line number/context are given by the backtrace.
- Remove over-specification of types (`&T` instead of
`&RWReadLockGuard`)
- Put reused values into constants
- `FromStr` instead of manual function
- Change `if let Some(()) = ...` to `if T.is_some()`