class virtualUse[['a, 'b]]start :object..end
inherit ['i, 'o] start to derive a class to represent the
initial state of a machine. It's start method initiates the machine
with the virtual private guard method.method private virtual guard : (< start : 'c. ('c, 'a, 'b, unit) Cf_state_gadget.t; .. >, 'a, 'b, unit)
Cf_state_gadget.guardmethod start : 'c. ('c, 'a, 'b, unit) Cf_state_gadget.tCf_state_gadget.start
Cf_state_gadget.guard self#guard self.