Fixes issue #3910's documentation gap. IsDefinedBy() returns
IfcRelDefinesByProperties relationship objects, not the property set
itself, and RelatingPropertyDefinition() must be used to reach the
IfcPropertySet or IfcElementQuantity. Properties can also come from an
element's type via IsTypedBy() -> RelatingType() -> HasPropertySets(),
a path that is easy to miss because it works differently. Adds a
worked, beginner-commented, compilable example covering both paths.
Generated with the assistance of an AI coding tool.
(cherry picked from commit 8fb8966094)
Petru Conduraru
7cf172b96b