== step =====
step =>> t1.step   (*  :  *)
  t1.stepO =>> t2.step   (*  :  *)
JOIN_stepO.J =>> stepO   (*  :  *)
== upd =====
upd =>> t1.upd   (*  :  *)
upd =>> t2.upd   (*  :  *)
== test =====
test =>> testO   (*  :  *)
== ctor =====
ctor =>> t1.ctor   (*  :  *)
ctor =>> t2.ctor   (*  :  *)
== init =====
init =>> t1.init   (*  :  *)
init =>> t2.init   (*  :  *)
