def __process_language_args(self, kwargs: T.Dict[str, T.List[mesonlib.FileOrString]]) -> None:
        """Convert split language args into a combined dictionary.

        The Meson DSL takes arguments in the form `<lang>_args : args`, but in the
        build layer we store these in a single dictionary as `{<lang>: args}`.
        This function extracts the arguments from the DSL format and prepares
        them for the IR.
        """
        d = kwargs.setdefault('depend_files', [])
        new_args: T.DefaultDict[str, T.List[str]] = collections.defaultdict(list)

        for l in compilers.all_languages:
            deps, args = self.__convert_file_args(kwargs[f'{l}_args'])
            new_args[l] = args
            d.extend(deps)
        kwargs['language_args'] = new_args
Convert split language args into a combined dictionary.

        The Meson DSL takes arguments in the form `<lang>_args : args`, but in the
        build layer we store these in a single dictionary as `{<lang>: args}`.
        This function extracts the arguments from the DSL format and prepares
        them for the IR.
        
mesonbuild/interpreter/interpreter.py