Add missing return types to Safe

[Uxio0]

No description provided.

[coveralls]

Pull Request Test Coverage Report for Build 10830033484

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
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Details

• 21 of 23 (91.3%) changed or added relevant lines in 2 files are covered.
• 3 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.06%) to 93.494%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
safe_eth/eth/ethereum_client.py	13	15	86.67%

Files with Coverage Reduction	New Missed Lines	%
safe_eth/eth/ethereum_client.py	1	85.67%
safe_eth/eth/clients/blockscout_client.py	2	93.94%

Totals
Change from base Build 10793540350:	-0.06%
Covered Lines:	8780
Relevant Lines:	9391

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💛 - Coveralls

[Uxio0]

@falvaradorodriguez added more fixes to EthereumClient

Please check the tests, it seems that the new assert does not work in all cases.

[Uxio0]

Sorry for the typo, fixed