`type t`
`val create : ?enabled:bool -> string -> t`

`create s` create and register a new logger named `s`

`val enable : label -> unit`

`enable "barname"` : enable the progress bar with label "barname"

`val pp_timer : Stdlib.Format.formatter -> t -> unit`
`val dump : Stdlib.Format.formatter -> unit -> unit`

print all timers that are enabled

`val start : t -> unit`
`val stop : t -> 'a -> 'a`
`val available : unit -> label list`

return the labels of all available progress bar