Add type annotation docs for PyGraph - #1685

Queue entry conditions

• any of [🔀 queue conditions]:
  • all of [📌 queue conditions of queue rule default]:
    • github-review-approved [🛡 GitHub branch protection]
    • any of [🛡 GitHub branch protection]:
      • check-success = Build Docs
      • check-neutral = Build Docs
      • check-skipped = Build Docs
    • any of [🛡 GitHub branch protection]:
      • check-success = Coverage
      • check-neutral = Coverage
      • check-skipped = Coverage
    • any of [🛡 GitHub branch protection]:
      • check-success = Build, rustfmt, and python lint
      • check-neutral = Build, rustfmt, and python lint
      • check-skipped = Build, rustfmt, and python lint
    • any of [🛡 GitHub branch protection]:
      • check-success = python3.12-x64 ubuntu-latest MSRV
      • check-neutral = python3.12-x64 ubuntu-latest MSRV
      • check-skipped = python3.12-x64 ubuntu-latest MSRV
• -closed [📌 queue requirement]
• -conflict [📌 queue requirement]
• -draft [📌 queue requirement]
• any of [📌 queue -> configuration change requirements]:
  • -mergify-configuration-changed
  • check-success = @mergify/Configuration changed
  • check-success = @mergify/Configuration has been deleted

You can queue this pull request now with @Mergifyio queue: it will enter the merge queue once these conditions match.