fields needs to be imported in examples

[chsachs]

neither attrs as a whole nor field is imported from attrs. Therefore the example using field does not work if one goes through the examples step by step. either import fields from the beginning (as suggested) or in the example using fields.

Summary

Pull Request Check List

• Added tests for changed code.
  Our CI fails if coverage is not 100%.
• New features have been added to our Hypothesis testing strategy.
• Changes or additions to public APIs are reflected in our type stubs (files ending in .pyi).
  • ...and used in the stub test file tests/typing_example.py.
  • If they've been added to attr/__init__.pyi, they've also been re-imported in attrs/__init__.pyi.
• Updated documentation for changed code.
  • New functions/classes have to be added to docs/api.rst by hand.
  • Changes to the signature of @attr.s() have to be added by hand too.
  • Changed/added classes/methods/functions have appropriate versionadded, versionchanged, or deprecated directives.
    Find the appropriate next version in our __init__.py file.
• Documentation in .rst files is written using semantic newlines.
• Changes (and possible deprecations) have news fragments in changelog.d.
• Consider granting push permissions to the PR branch, so maintainers can fix minor issues themselves without pestering you.

[Tinche]

I would prefer if you imported field when it's used for the first time. Think it keeps the flow better.

[hynek]

I would prefer if you imported field when it's used for the first time. Think it keeps the flow better.

I 100% agree in general, but I think it's fair enough to import the two most important functions at once.

[hynek]

Thanks!