Macro lab_grader::yaml

macro_rules! yaml {
    ( $file:expr ) => { ... };
}

This is an important macro. It reads data from a file using the include_bytes! macro. When compiling for debug, this will read from the filesystem. When compiling for release, this will embed the data in the executable. Graders built using this crate need to have the data embedded in the executable to make it easier to distribute and to keep the data private.