My question is in the title.

In the tutorial, I read: Use 'pass' in places, where code is required syntactically, but none is needed.
In order to save indentations, I used the conditional assignement in some segment of code. But I only want to include z in the set x, if it is not None, because later, the None disturbs.

So my thesis is: The code in the title is syntactically correct, but still, I get a syntax error.

Thank you for your kind consideration