How to check whether a variable is a class or not

Question

I was wondering how to check whether a variable is a class (not an instance!) or not.

I've tried to use the function isinstance(object, class_or_type_or_tuple) to do this, but I don't know what type would a class will have.

For example, in the following code

class Foo: pass  
isinstance(Foo, **???**) # i want to make this return True.

I tried to substitute "class" with ???, but I realized that class is a keyword in python.