`generator` methods of operators should return new opmath instances

[PietropaoloFrisoni]

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Codecov Report

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

Project coverage is 99.63%. Comparing base (f9bdb32) to head (0625c82). Report is 3 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5253      +/-   ##
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- Coverage   99.65%   99.63%   -0.02%     
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  Files         399      400       +1     
  Lines       36901    36746     -155     
==========================================
- Hits        36774    36613     -161     
- Misses        127      133       +6     

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[PietropaoloFrisoni]

When tests all pass happy to approve :)

All tests were totally fine. Now there's an error associated with an external library that has most probably nothing to with the PR since, from what I can see, it is present in other PRs as well (I'll figure out what's going on)

Can you make sure to follow up on updating also the qchem generators?

@Qottmann Sure, I'll replace the generators in qchem after solving the two related issues in tapering. I'll create a story for that to make sure we do not forget.

[trbromley]

Will the return type of generator depend on whether new opmath is enabled? Or are we always returning the new type?

[PietropaoloFrisoni]

Will the return type of generator depend on whether new opmath is enabled? Or are we always returning the new type?

Since qml.s_prod always returns a SProd instance (regardless of whether new opmath is enabled), the generators should always be returned as a new opmath instance.