Fix#17

[codecov[bot]]

Codecov Report

Base: 58.26% // Head: 61.25% // Increases project coverage by +2.98% :tada:

Coverage data is based on head (d43f05e) compared to base (e9d4d42). Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #18 +/- ## ========================================== + Coverage 58.26% 61.25% +2.98% ========================================== Files 19 19 Lines 623 622 -1 ========================================== + Hits 363 381 +18 + Misses 260 241 -19 ``` | [Impacted Files](https://codecov.io/gh/jedie/pysmartmeter/pull/18?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Jens+Diemer) | Coverage Δ | | |---|---|---| | [pysmartmeter/data\_classes.py](https://codecov.io/gh/jedie/pysmartmeter/pull/18?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Jens+Diemer#diff-cHlzbWFydG1ldGVyL2RhdGFfY2xhc3Nlcy5weQ==) | `92.00% <100.00%> (+10.00%)` | :arrow_up: | | [pysmartmeter/utilities/credentials.py](https://codecov.io/gh/jedie/pysmartmeter/pull/18?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Jens+Diemer#diff-cHlzbWFydG1ldGVyL3V0aWxpdGllcy9jcmVkZW50aWFscy5weQ==) | `100.00% <100.00%> (+70.00%)` | :arrow_up: | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Jens+Diemer). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Jens+Diemer)

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