Address code style issues

[achilleas-k]

From the LGTM bot in PR #20.

This pull request introduces 8 alerts when merging 3d7377b into 6916644 - view on LGTM.com

new alerts:

• 3 for Unused local variable
• 1 for Wrong name for an argument in a call
• 1 for Module is imported more than once
• 1 for Unused import
• 1 for Variable defined multiple times
• 1 for Wrong name for an argument in a class instantiation

Originally posted by @lgtm-com in #20 (comment)