def _normalize_file_paths(self, *args):
        """Returns all given configuration file paths as one list."""
        paths = []
        for arg in args:
            if arg is None:
                continue
            elif self._is_valid_file(arg):
                paths.append(arg)
            elif isinstance(arg, list) and all(self._is_valid_file(_) for _ in arg):
                paths = paths + arg
            elif not self.ignore_errors:
                raise TypeError('Config file paths must be string path or list of paths!')
        return paths
Returns all given configuration file paths as one list.