I know this question has been asked before, but the fix for it didn't apply to my code. The code is very simple, and I don't know what's happening.

What's supposed to happen is then when the button is pressed, it runs the hello() function, which adds a label to the screen saying You Pressed me!. But, an error pops up saying AttributeError: 'NoneType' object has no attribute 'set_color_mode'.

Here is my code:

import py_cui

root = py_cui.PyCUI(14, 18)

def hello():
    root.add_label("You Pressed me!", 0, 0)

button = root.add_button('Button Text', 1, 2, column_span=2, command=hello())
root.start()