A "pdbx_vrpt_model_list" is one of the structures that are described by a PDB entry. 
            Most NMR entries as well as some entries determined by other experimental techniques, 
            contain an ensemble of models (structures). For most NMR entries, the models should be 
            chemically identical - i.e., contain the exact same atoms, and will only differ
            in the cartesian coordinates of constituent atoms. For older NMR entries, and 
            for non-NMR entries, this is not enforced.