reserve y for set;
reserve A for Category,
  a,o for Object of A;
reserve f for Morphism of A;

theorem Th3:
  for f being Element of the carrier' of A holds [[<|cod f,?>,<|dom
  f,?>],<|f,?>] is Element of the carrier' of Functors(A,EnsHom(A))
proof
  let f be Element of the carrier' of A;
  <|cod f,?> is_naturally_transformable_to <|dom f,?> by Th2;
  then [[<|cod f,?>,<|dom f,?>],<|f,?>] in NatTrans(A,EnsHom(A)) by
NATTRA_1:def 16;
  hence thesis by NATTRA_1:def 17;
end;
