Function getDataProperty

Reads a single named property out of a DataObject's PropertySets.

Helper for IfcPropertyRule predicates — most common pattern is "this object's Pset_WallCommon.IsExternal is true" and writing the lookup inline is verbose. Pass the PropertySet's type (the IFC pset name, e.g. "Pset_WallCommon") and the property's name (e.g. "IsExternal").

Returns undefined when:

• dataObject is undefined
• the object has no propertySets
• no PropertySet matches propertySetType
• the matched PropertySet has no property named propertyName

Property-set matching is exact on PropertySet.type. If you need fuzzier lookup (e.g. case-insensitive pset name) walk the propertySets array yourself.