I learned about type aliases on the page（https://docs.python.org/3/library/typing.html）, and I found that following the code (Vector = list[float])in the tutorial, an error occurred (NameError: name 'typing' is not defined) when running.

The following code has the same problem：
  ConnectionOptions = dict[str, str]
  Address = tuple[str, int]
  Server = tuple[Address, ConnectionOptions]

I searched through google and found the correct code：
  from typing import List
  Vector = List[float]

  from typing import Dict, Tuple, Sequence
 
  ConnectionOptions = Dict[str, str]
  Address = Tuple[str, int]
  Server = Tuple[Address, ConnectionOptions]

What version of Python did you use? This is a documentation for Python 3.9.

I am using python3.8, it turned out to be a version issue, sorry

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发件人:                                                                                                                        "Python tracker"                                                                                    <report@bugs.python.org&gt;;
发送时间:&nbsp;2021年1月12日(星期二) 晚上10:50
收件人:&nbsp;"破碎的冰"<Smile_zjk@qq.com&gt;;

主题:&nbsp;[issue42910] Wrong code appears in the type alias introduction

Serhiy Storchaka <storchaka+cpython@gmail.com&gt; added the comment:

What version of Python did you use? This is a documentation for Python 3.9.

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nosy: +serhiy.storchaka

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<https://bugs.python.org/issue42910&gt;
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