Rust extension hook that can be required.
Files are mounted in the interpreter filesystem and can modify interpreter
state when they are loaded.
Concrete type for interpreter.
Concrete error type for eval functions.
Called when the filename mapped to this type is required by the VM.
This function can mutate interpreter state, such as defining classes and modules. This function is equivalent to the "init" methods of C-implemented Rubygems.
If a fallible API on the interpreter returns an error, implementors
should return an error. Example fallible APIs that might be called on