docs: def parse_relation(obj: dict) -> BioCRelation:
      """Deserialize a dict obj to a BioCRelation object"""
      rel = BioCRelation()
      rel.id = obj['id']
      rel.infons = obj['infons']
      for node in obj['nodes']:
          rel.add_node(BioCNode(node['refid'], node['role']))
      return rel