sock_merchant.py: Matching socks by color (#5761)

* Python file for finding number of pairs

* updating DIRECTORY.md

* fixed iterative_pair.py

* further fixed with type casting

* fixed naming conventions

* further fixed with naming convention

* documented done

* build issue fixed

* updating DIRECTORY.md

* Revert "documented done"

This reverts commit 3be15ca374f3ea3f01f725912dba59b939b058b5.

* Update canny.py

* Update test_digital_image_processing.py

* Update sobel_filter.py

* requirements.txt fixed

* keras<2.7.0

* Update sock_merchant.py

* doctest with black fixed

* Update sock_merchant.py

Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
Co-authored-by: Christian Clauss <[email protected]>