Creates the cache directory if it doesn't already exist. Returns the
        full path to the specified file inside the cache directory.

def _get_path(self, file):
        """Creates the cache directory if it doesn't already exist. Returns the
        full path to the specified file inside the cache directory."""
        dir = self._cache_directory()
        if not os.path.exists(dir):
            os.makedirs(dir)
        return os.path.join(dir, file)