Add a callback or a collection of callbacks to a callback list.
Disable a callback list from doing anything more.
Determine if the callbacks list has been disabled.
Remove all of the callbacks from a list.
Call all of the callbacks with the given arguments.
Call all callbacks in a list with the given context and arguments.
Determine if the callbacks have already been called at least once.
callback is in a list.
Determine whether or not the list has any callbacks attached.
Lock a callback list in its current state.
Determine if the callbacks list has been locked.
Remove a callback or a collection of callbacks from a callback list.