- max_id: current max value of id in storage (useful to understand next id)
- num_ignored: the number of ids that were ignored by
ignore_kth_same_point
- unlearner's status: See jubatus/jubatus_core#166
- num_id_master: number of ids in
lof_storage::_lof_table
- num_id_diff: number of ids in
lof_storage::_lof_table_diff