docs: function (value) {
        if (fp.is(String, value) && value.indexOf(':') > 0) {
          let [path, id] = value.split(':');
          return { _id: value, _type: path, [options.idField]: id };
        } else {
          // keep original value in _value
          return { _id: value, _type: value, [options.idField]: null, _value: value };
        }
      }