chore: more specific return type for chunk() method

[rela589n]

Follows from #350

[what-the-diff]

PR Summary

• Modified Return Type in chunk Method
  This PR updates the type of data that the chunk method returns. Previously, it could return a list that might be empty. Now, it ensures that the list returned will always contain at least one item. This adjustment improves the method's reliability and predictability in our system.

[drupol]

I think there are some new errors to fix.

[rela589n]

Do you mean this CI error?

Unfortunately I could not get my local environment ready for the development (If I remember correctly, if I try to run tests on the main branch, some of them fail) yet

[rela589n]

@drupol , I have slightly changed the variables names here, since it took me around 15 minutes to figure out what $i, $values, and $sizes variables mean and what the code below does. If you wish, I could revert it back to the previous version, but in my opinion the current implementation is better

[drupol]

No no it's fine, it's actually a good idea.

[rela589n]

without this @var annotation psalm won't be able to infer the fact that chunk is never empty when it is yielded

[rela589n]

@drupol , frankly speaking I have no clue what these errors are all about