Handle sensor list in topic

[ninahakansson]

In case of list of sensor, use MULTIPLE_SENSORS in topic. We do not want a tuple or lsit in the publishing topic.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 91.26%. Comparing base (80956c4) to head (81ff0e6). Report is 2 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #154 +/- ## ========================================== + Coverage 91.23% 91.26% +0.02% ========================================== Files 32 32 Lines 4417 4429 +12 ========================================== + Hits 4030 4042 +12 Misses 387 387 ``` | [Flag](https://app.codecov.io/gh/pytroll/pytroll-collectors/pull/154/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pytroll) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/pytroll/pytroll-collectors/pull/154/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pytroll) | `91.26% <100.00%> (+0.02%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pytroll#carryforward-flags-in-the-pull-request-comment) to find out more.

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[coveralls]

Pull Request Test Coverage Report for Build 8799660697

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 0.0%

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Totals
Change from base Build 7932120988:	0.0%
Covered Lines:	0
Relevant Lines:	0

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💛 - Coveralls

[ninahakansson]

Unfortunately isinstance("atms", collections.abc.Sequence) is also True ...