Fixed Code Quality Issues

[HarshCasper]

Description

• Fixed the use of hasattr
• Fixed unnecessary use of getattr
• Fixed method with no argument
• Fixed multiple import name
• Add .deepsource.toml

I ran a DeepSource Analysis on my fork of this repository. You can see all the issues raised by DeepSource here.

DeepSource helps you to automatically find and fix issues in your code during code reviews. This tool looks for anti-patterns, bug risks, performance problems, and raises issues. There are plenty of other issues in relation to Bug Discovery and Anti-Patterns which you would be interested to take a look at.

If you do not want to use DeepSource to continuously analyze this repo, I'll remove the .deepsource.toml from this PR and you can merge the rest of the fixes. If you want to setup DeepSource for Continuous Analysis, I can help you set that up.

[ionelmc]

Please don't touch the tests, callable(something) is not the same as hasattr(something, '__call__'). The later invokes descriptor protocol while callable just does a super optimized and incorrect slot check.