human
I wrote the below code

    def decorate(fn):
        existing = class_.__dict__.get('_compiler_dispatcher', None)
        existing_dispatch = getattr(class_, '_compiler_dispatch', None)
        if (not existing):
            existing = _dispatcher()
            if existing_dispatch:
                def _wrap_existing_dispatch(element, compiler, **kw):
                    try:
                        return existing_dispatch(element, compiler, **kw)
                    except exc.UnsupportedCompilationError:
                        raise exc.CompileError(('%s    construct    has    no    default    compilation    handler.' % type(element)))
                existing.specs['default'] = _wrap_existing_dispatch
            setattr(class_, '_compiler_dispatch', (lambda *arg, **kw: existing(*arg, **kw)))
            setattr(class_, '_compiler_dispatcher', existing)
        if specs:
            for s in specs:
                existing.specs[s] = fn
        else:
            existing.specs['default'] = fn
        return fn
    return decorate

What's a good function header?
 ... Here's a good function header?
assistant
#Here's a good function header.

def compiles(class_, *specs):