Problem running Python program in MatLab "Undefined variable" and "or class" py.our_module.our_script.our_function "."

I have MatLab 2017b. I followed the example of the following video to the letter:

link

I even downloaded without altering the code provided by the author of the video in the description:

link

import numpy

def our_function(text):
    print('%s %f' % (text, numpy.nan))

but when executing in MatLab the exact code that executes in the video (see minute 1:05 of the video) I have the following:

>> py.our_module.our_script.our_function('yolo')
Undefined variable "py" or class
"py.our_module.our_script.our_function".

Then verify what is described on the following page:

link

but it did not help at all, does anyone have any idea what is going on? or to explain a simple way to run Python code in MatLab.

I give thanks in advance to all who respond.