docs: def _read_models(self, graph):
          """
          Read graph and add models to document
          """
          for e in self._get_elements(graph, SBOL.Model):
              identity = e[0]
              m = self._get_rdf_identified(graph, identity)
              m['source'] = self._get_triplet_value(graph, identity, SBOL.source)
              m['language'] = self._get_triplet_value(graph, identity, SBOL.language)
              m['framework'] = self._get_triplet_value(graph, identity, SBOL.framework)
              obj = Model(**m)
              self._models[identity.toPython()] = obj
              self._collection_store[identity.toPython()] = obj