Example of a case where declaring variable inside __init__ is bad

Python
4

Directly from the documentation you linked:

class Dog:

    kind = 'canine'         # class variable shared by all instances

    def __init__(self, name):
        self.name = name    # instance variable unique to each instance

You aren’t seeing this issue because you only have one instance of your class, but the documentation is still accurate. You should only put variable declarations in the class definition outside of methods when you want to share the data across all instances.