Example code doesn't work on python 3.9

[churnikov]

I get the following error when I'm trying to run your example code with python 3.9

Code:

import typedparse
from typing import Optional


def main(file: str, number: Optional[int] = 6):
    """Display first lines of a file.

    Args:
        file: file to display
        number: number of lines to display
    """
    with open(file, "r") as f:
        for i in range(0, number):
            print(f.readline(), end="")


if __name__ == "__main__":
    typedparse.parse(main, generate_short_flags=True)

Error:

Traceback (most recent call last):
  File "/Users/nikita/Projects/personal/keynote-highlight/keynote_highlight/main.py", line 56, in <module>
    typedparse.parse(main, generate_short_flags=True)
  File "/Users/nikita/Library/Caches/pypoetry/virtualenvs/keynote-highlight-P7sqe0O--py3.9/lib/python3.9/site-packages/typedparse/__init__.py", line 27, in parse
    return ArgParserFactory(generate_short_flags=generate_short_flags).create(obj).parse()
  File "/Users/nikita/Library/Caches/pypoetry/virtualenvs/keynote-highlight-P7sqe0O--py3.9/lib/python3.9/site-packages/typedparse/argparse.py", line 132, in create
    return ArgParserLeaf(self._parser, obj, self._generate_short_flags)
  File "/Users/nikita/Library/Caches/pypoetry/virtualenvs/keynote-highlight-P7sqe0O--py3.9/lib/python3.9/site-packages/typedparse/argparse.py", line 90, in __init__
    kwargs.update(type=type_func or spec.get_class(tpe))
  File "/Users/nikita/Library/Caches/pypoetry/virtualenvs/keynote-highlight-P7sqe0O--py3.9/lib/python3.9/site-packages/typedparse/spec.py", line 180, in get_class
    m = getattr(m, comp)
AttributeError: module 'typing' has no attribute 'Optional[int]'

Process finished with exit code 1

[khud]

Thanks a lot!