docs: def _read_sequences(self, graph):
          """
          Read graph and add sequences to document
          """
          for e in self._get_elements(graph, SBOL.Sequence):
              identity = e[0]
              c = self._get_rdf_identified(graph, identity)
              c['elements'] = self._get_triplet_value(graph, identity, SBOL.elements)
              c['encoding'] = self._get_triplet_value(graph, identity, SBOL.encoding)
              seq = Sequence(**c)
              self._sequences[identity.toPython()] = seq
              self._collection_store[identity.toPython()] = seq