[mypy] Fix type annotations for stack_using_dll.py

[archaengel]

$git checkout mypy-fix-stack-dll
Switched to branch 'mypy-fix-stack-dll'

$ mypy --ignore-missing-imports data_structures/stacks/stack_using_dll.py --strict
Success: no issues found in 1 source file

$ mypy --ignore-missing-imports data_structures/stacks --strict > after.txt

$ git checkout master
Switched to branch 'master'

$ mypy --ignore-missing-imports data_structures/stacks --strict > before.txt

$ diff before.txt after.txt
5,28d4
< data_structures/stacks/stack_using_dll.py:6: error: Function is missing a type annotation
< data_structures/stacks/stack_using_dll.py:38: error: Function is missing a return type annotation
< data_structures/stacks/stack_using_dll.py:38: note: Use "-> None" if function does not return a value
< data_structures/stacks/stack_using_dll.py:41: error: Function is missing a type annotation
< data_structures/stacks/stack_using_dll.py:44: error: Call to untyped function "Node" in typed context
< data_structures/stacks/stack_using_dll.py:46: error: Call to untyped function "Node" in typed context
< data_structures/stacks/stack_using_dll.py:52: error: Function is missing a return type annotation
< data_structures/stacks/stack_using_dll.py:62: error: Function is missing a return type annotation
< data_structures/stacks/stack_using_dll.py:64: error: Item "None" of "Optional[Any]" has no attribute "data"
< data_structures/stacks/stack_using_dll.py:66: error: Function is missing a return type annotation
< data_structures/stacks/stack_using_dll.py:74: error: Function is missing a return type annotation
< data_structures/stacks/stack_using_dll.py:77: error: Function is missing a return type annotation
< data_structures/stacks/stack_using_dll.py:77: note: Use "-> None" if function does not return a value
< data_structures/stacks/stack_using_dll.py:89: error: Call to untyped function "Stack" in typed context
< data_structures/stacks/stack_using_dll.py:93: error: Call to untyped function "push" in typed context
< data_structures/stacks/stack_using_dll.py:96: error: Call to untyped function "push" in typed context
< data_structures/stacks/stack_using_dll.py:99: error: Call to untyped function "push" in typed context
< data_structures/stacks/stack_using_dll.py:102: error: Call to untyped function "push" in typed context
< data_structures/stacks/stack_using_dll.py:105: error: Call to untyped function "print_stack" in typed context
< data_structures/stacks/stack_using_dll.py:108: error: Call to untyped function "top" in typed context
< data_structures/stacks/stack_using_dll.py:114: error: Call to untyped function "pop" in typed context
< data_structures/stacks/stack_using_dll.py:117: error: Call to untyped function "pop" in typed context
< data_structures/stacks/stack_using_dll.py:120: error: Call to untyped function "print_stack" in typed context
< data_structures/stacks/stack_using_dll.py:123: error: Call to untyped function "is_empty" in typed context
85c61
< Found 82 errors in 12 files (checked 13 source files)
---
> Found 60 errors in 11 files (checked 13 source files)

Related to #4052

Describe your change:

Add generic type annotations to stack_using_dll.py.

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• Documentation change?

Checklist:

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• All new Python files are placed inside an existing directory.
• All filenames are in all lowercase characters with no spaces or dashes.
• All functions and variable names follow Python naming conventions.
• All function parameters and return values are annotated with Python type hints.
• All functions have doctests that pass the automated testing.
• All new algorithms have a URL in its comments that points to Wikipedia or other similar explanation.
• If this pull request resolves one or more open issues then the commit message contains Fixes: #{$ISSUE_NO}.

[poyea]

Thank you for your pull request!🤩

[archaengel]

Thanks for your review! 😸

[cclauss]

Rock and roll!