Pruner does not run in Python 3.7.x

[adhocmaster]

Describe the issue: Literal is not available in the typing package of Python 3.7.x's. It can be fixed by importing from typing_extensions package.

\anaconda3\envs\compression\lib\site-packages\nni\compression\base\config.py in <module>
      7 from copy import deepcopy
      8 import re
----> 9 from typing import Any, Dict, List, Literal, Tuple
     10 
     11 from schema import Schema, Optional, Or

ImportError: cannot import name 'Literal' from 'typing' (...\lib\typing.py)

Environment:

• NNI version: 3.0
• Training service (local|remote|pai|aml|etc): local
• Client OS: windows 10
• Server OS (for remote mode only):
• Python version: 3.7.9
• PyTorch/TensorFlow version: 1.11.0
• Is conda/virtualenv/venv used?: conda
• Is running in Docker?: No

Configuration:

• Experiment config (remember to remove secrets!): config_list = [{ 'op_types': ['Linear', 'Conv2d'], # types of layers to prune 'exclude_op_names': ['fc3'], # exclude specific layers 'sparse_ratio': 0.3 # mask 30% of the parameters }]
• Search space:

Log message:

• nnimanager.log:
• dispatcher.log:
• nnictl stdout and stderr:

How to reproduce it?: