Added typing to examples

[WisdomPill]

I forgot to create a pull request for this, I do not know if it is welcome or useful by any means.
I fell that people would start using types more often, it saves us from some difficult to find bugs, so why not show it.

What do these changes do?

Add type hints to examples so that it is easier to get up and going with typed code

Are there changes in behavior for the user?

Not really

Checklist

• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes
• If you provide code modification, please add yourself to CONTRIBUTORS.txt
  • The format is <Name> <Surname>.
  • Please keep alphabetical order, the file is sorted by names.
• Add a new news fragment into the CHANGES folder
  • name it <issue_id>.<type> for example (588.bugfix)
  • if you don't have an issue_id change it to the pr id after creating the pr
  • ensure type is one of the following:
    • .feature: Signifying a new feature.
    • .bugfix: Signifying a bug fix.
    • .doc: Signifying a documentation improvement.
    • .removal: Signifying a deprecation or removal of public API.
    • .misc: A ticket has been closed, but it is not of interest to users.
  • Make sure to use full sentences with correct case and punctuation, for example: "Fix issue with non-ascii contents in doctest text files."

[WisdomPill]

I do not know what kind of change I should add in CHANGES, @asvetlov do you have any suggestions?

[lgtm-com]

This pull request introduces 4 alerts when merging 9f08ad1 into 37d2376 - view on LGTM.com

new alerts:

• 2 for Module is imported with 'import' and 'import from'
• 1 for Unused local variable
• 1 for Unused import

[asvetlov]

I think we don't need a CHANGES file for this PR but the linter check should be green.
This is the pre-requirement for merging.

[WisdomPill]

I am on it, a new commit is coming

[lgtm-com]

This pull request introduces 1 alert and fixes 1 when merging c3dc373 into 5357858 - view on LGTM.com

new alerts:

• 1 for Module is imported with 'import' and 'import from'

fixed alerts:

• 1 for Module is imported with 'import' and 'import from'

[codecov]

Codecov Report

Merging #5256 (e63ef8b) into master (37d2376) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #5256   +/-   ##
=======================================
  Coverage   97.54%   97.54%           
=======================================
  Files          43       43           
  Lines        8794     8794           
  Branches     1413     1415    +2     
=======================================
  Hits         8578     8578           
  Misses        101      101           
  Partials      115      115           

Flag	Coverage Δ
unit	97.37% <ø> (-0.03%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
aiohttp/test_utils.py	99.68% <0.00%> (ø)

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[lgtm-com]

This pull request fixes 1 alert when merging e63ef8b into 5357858 - view on LGTM.com

fixed alerts:

• 1 for Module is imported with 'import' and 'import from'

[asvetlov]

Thanks!