createRelativePosition = (type, item, assoc) => {
  let typeid = null;
  let tname = null;

  if (type._item === null) {
    tname = findRootTypeKey(type);
  } else {
    typeid = createID(type._item.id.client, type._item.id.clock);
  }

  return new RelativePosition(typeid, tname, item, assoc);
}
@param {AbstractType<any>} type
@param {ID|null} item
@param {number} [assoc]

@function