fix: handle identifiers in subscript

[elsapet]

Description

If there is an identifier in the subscript, we want to track this back to its origin

With this change, we can now pick up both of these cases:

globals()[input()] # no identifier

x = input()
globals()[x] # identifier

Checklist

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• I've added test coverage that shows my fix or feature works as expected.
• I've updated or added documentation if required.