Processing timememory output data takes too long

[glpuga]

Bug description

Processing output timemory jsons for long runs takes so long it appears lambkin just froze.

This is only made worse by #95 , because you need to choose the least of two evils to be able to do any change.

Platform (please complete the following information):

• OS: [e.g. Ubuntu Focal]
• Python version: [e.g. 3.8]
• lambkin version: [e.g. tag, commit sha]

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1. ...

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Expected behavior
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Actual behavior
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Additional context

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