fix lint errors

[metskem]

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Description of the Change

Fix lint errors.

• imports ordering/grouping
• redundant null check
• unused function
• unchecked errors

Why Is This PR Valuable?

So, you can do a successful "make" .

Why Should This Be In Core?

So you can make lint.

Applicable Issues

none

How Urgent Is The Change?

Not urgent

Other Relevant Parties

everyone that runs the lint checks