This error is intended for cases when a method is
intentionally not implemented, because the module/class defining
it expects a subclass (or class including the module) to implement
the method.
This is intended to distinguish it from other cases, such as:
* feature not implemented yet
* edge case of a method call not yet supported
Notably it avoids the misuse of the Ruby-defined NotImplementedError,
which is only intended for much more specific scenarios:
> Raised when a feature is not implemented on the current platform. For example, methods depending on the fsync or fork system calls may raise this exception [...]
Also see https://docs.ruby-lang.org/en/master/NotImplementedError.html
Jan Sandbrink