YANG defines distinct equality classes based on whether order of items is significant. This is typically expressed via 'ordered-by' statement.

Our NormalizedNode model does not correctly capture this property, leading to ill-defined equality contract where MapNode and LeafSetNode are involved.

Define a general ItemOrder construct with two subclasses, Ordered and Unordered, which capture this contract. These need to be mutally-exclusive similar to Mutable/Immutable contract.