from typing import Union, Optional, Callable, Iterable, Mapping, Sequence, List, Tuple, Any
https://docs.python.org/3/library/typing.html
Any, Union, Tuple, List, Sequence, Mapping, Callable, TypeVar,Optional, Generic等的使用频率比较高，其中Union、Optional、Sequence、Mapping非常有用。
- Union
即并集，所以Union[X, Y] 意思是要么X类型、要么Y类型
- Optional
Optional[X]与Union[X, None]，即它默认允许None类型
- Sequence
即序列，需要注意的是，List一般用来标注返回值；Sequence、Iterable用来标注参数类型
- Mapping
即字典，需要注意的是，Dict一般用来标注返回值；Mapping用来标注参数类型
def test(
X: Optional[Union[np.ndarray, pd.DataFrame]] = None,
obs: Optional[Union[pd.DataFrame, Mapping[str, Iterable[Any]]]] = None,
var: Optional[Union[pd.DataFrame, Mapping[str, Iterable[Any]]]] = None,
uns: Optional[Mapping[str, Any]] = None,
obsm: Optional[Union[np.ndarray, Mapping[str, Sequence[Any]]]] = None,
varm: Optional[Union[np.ndarray, Mapping[str, Sequence[Any]]]] = None,
layers: Optional[Mapping[str, Union[np.ndarray, sparse.spmatrix]]] = None,
raw: Optional[Raw] = None,
dtype: Union[np.dtype, str] = 'float32',
shape: Optional[Tuple[int, int]] = None,
filename: Optional[PathLike] = None,
filemode: Optional[str] = None,
asview: bool = False,
*, oidx: Index = None, vidx: Index = None) -> List[Any]:
pass