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Explicit isotope labels disappear from atom keys · case 05

Explicit isotope labels disappear from atom keys.

Member previewVariant 5 · 3 implementations · 6 checks per implementation

Case contract

Return [element, isotope] exactly; None means unspecified and integer zero means an explicit model sentinel.

Why this case matters

Controlled molecular graph interchange model; tests isolate atom or bond representation errors without claiming chemical validity or production toolkit equivalence.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
varying isotope	`["C", null]`	`["C", 17]`	Failed

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