
theorem
  for A,B be transitive with_units non empty AltCatStr, F1,F2 be
covariant Functor of A,B holds F1 is_naturally_transformable_to F2 implies for
t being natural_transformation of F1,F2 holds (idt F2)`*`t = t & t`*`(idt F1) =
  t
by Th5;
