`sig
type t = USB.request
val get_status : USB.Request.t
val clear_feature : USB.Request.t
val set_feature : USB.Request.t
val set_address : USB.Request.t
val get_descriptor : USB.Request.t
val set_descriptor : USB.Request.t
val get_configuration : USB.Request.t
val set_configuration : USB.Request.t
val get_interface : USB.Request.t
val set_interface : USB.Request.t
val synch_frame : USB.Request.t
end`