Unintended Boolean Conversions and Ordering Changes in `IndexMap`

[M-Lampert]

Due to the new internal representation of node_ids in IndexMap as numpy.array, there are sometimes some unintended conversions from integers to booleans happening. I also noticed that the ordering of strings is sometimes different than what was inserted at the beginning.

This was first encountered by @lisiq and @chrisbloecker. Maybe the have some more details on this.