Limit access to a class function to child classes that inherit from the class

Question

I have a use case where there are some attributes that are common to different categories that I capture through a base class and then there are some category specific parameters that are assigned in the child class definitions. For example,

class Parent:
    def __init__(self):
        self.category_param = None

    def run_category(self):
        self.category_param.run()

class Child(Parent):
    def __init__(self, cat_param):
        super(Child, self).__init__()
        self.category_param = cat_param

Although the function run_category has the same form for all instantiations of class Child, it does use a category specific param that is None/undefined in class Parent.

I am looking for a clean way to prevent being able to call run_category() from an instantiation of class Parent.

parent = Parent()
parent.run()    # Should throw an error

I would like the above code to throw an error message that I have control over (since the error message None has no attribute run() is undesirable and would be the current way the above code crashes).

A possibility is of course to define run_category as,

def run_category(self):
    if self.category_param is not None:
        self.category_param.run()
    else:
        raise NotImplementedError("method run() is not available for abstract base class Parent")

but I was looking for something cleaner/more pythonic.