?
Chaining results using match can get pretty untidy; luckily, the ? operator
can be used to make things pretty again. ? is used at the end of an expression
returning a Result, and is equivalent to a match expression, where the
Err(err) branch expands to an early return Err(From::from(err)), and the Ok(ok)
branch expands to an ok expression.
Be sure to check the documentation,
as there are many methods to map/compose Result.