def sub(self, name, contents=None):
        path = os.path.join(self.path, name)
        if contents:
            with open(path, 'wb') as f:
                f.write(contents)
        return path
Get a path to a file named `name` inside this temporary
dataset/ETHPy150Open sampsyo/confit/test/__init__.py/TempDir.sub