Function build_export_model 

pub fn build_export_model(content: &[u8]) -> ExportModel

Build the export model from raw IFC/STEP bytes.

Collects every row into an ExportModel. This is fine for normal models, but for very large ones (tens of millions of entities) the retained Vec<EntityRow> is itself multiple GB — prefer stream_export_model, which yields rows one at a time and never holds them all. build_export_model is a thin collect over stream_export_model, so the two share one code path.