fix anti-patterns and optimize code performance

This PR includes:

using is instead of ==
- It is recommended to use identity test ( is ) instead of equality test ( == ) when you need to compare types of two objects.
Comparisons to the singleton objects, like True, False, and None, should be done with identity, not equality. Use “is” or “is not”. Identity checks are faster than equality checks.
replaced iterating the dictionary directly instead of calling .keys(). Using for key in dictionary would always iterate the dictionary keys.
remove unused imported modules.

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