Do commands only works when I use it directly with dialogue. What I´m doing wrong?

[GitFula]

So this works

~ start
System: Leave the area?

• Yes.
  System: ... [do Funciones.show_end_stage()]

but stuff like

~ start
System: Leave the area?

• Yes.
  [do Funciones.show_end_stage()] or

~ start
System: Leave the area?

• Yes. [do Funciones.show_end_stage()]

wont work. I have seen it used it that way on the examples. What I´m doing wrong??