755.hlean:56:10: warning: using 'sorry'
755.hlean:57:10: warning: using 'sorry'
755.hlean:58:10: warning: using 'sorry'
LEAN_INFORMATION
position 55:52
A : Type,
B : Type,
f : one_step_tr A → B
⊢ Π (x y : A),
    f (tr x) = f (tr y)
END_LEAN_INFORMATION