<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def save(self, output: Union[str, BinaryIO], series: Optional[str] = None, deps: Iterable=tuple(), create_missing_dirs: bool=True) -> "Model": """ Serialize the model to a file. :param output: Path to the file or a file object. :param series: Name of the model series. If it is None, it will be taken from \ the current value; if the current value is empty, an error is raised. :param deps: List of the dependencies. :param create_missing_dirs: create missing directories in output path if the output is a \ path. :return: self """

        check_license(self.license)
        if series is None:
            if self.series is None:
                raise ValueError("series must be specified")
        else:
            self.series = series
        if isinstance(output, str) and create_missing_dirs:
            dirs = os.path.split(output)[0]
            if dirs:
                os.makedirs(dirs, exist_ok=True)
        self.set_dep(*deps)
        tree = self._generate_tree()
        self._write_tree(tree, output)
        self._initial_version = self.version
        return self