Definition of natural output in code

Dear prof. Pfeifer,

May I ask something in your code implementation for Gali (2015) chapter 3? In there, you have the following definition of natural output:

[name='Definition natural output, eq. (20)']

Is seems it should be y_nat=psi_n_ya*a + psi_y;. In the book, we have y_t^n = \psi_{ya} a_t + \psi_y, \;\;\psi_y>0. Or \psi_y is very small to matter?

As the introductory note states, all variables are in deviations from the steady state in my implementation.\psi_y is the steady state and therefore left out.