* added mutable default args * most of the Bs * add comment about lrucache * b905 old-commit-hash: e4ead4f1830618f5f61978491930cb0b8d36ab26
* added mutable default args * most of the Bs * add comment about lrucache * b905 old-commit-hash: e4ead4f1830618f5f61978491930cb0b8d36ab26