Fixing returning types

[eduard13]

Description (*)

This PR fixes the returning types for some methods

Fixed Issues (if relevant)

N/A

Manual testing scenarios (*)

N/A

Contribution checklist (*)

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)

[magento-engcom-team]

Hi @eduard13. Thank you for your contribution
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[magento-engcom-team]

Hi @dmytro-ch, thank you for the review.
ENGCOM-4194 has been created to process this Pull Request

[ghost]

Hi @eduard13, thank you for your contribution!
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