base_class()
Instance Public methods
Returns the class descending directly from ActiveRecord::Base, or an abstract class, if any,
in the inheritance hierarchy.
If A extends AR::Base, A.base_class will return
A. If B descends from A through some arbitrarily deep hierarchy,
B.base_class will return A.
If B < A and C < B and if A is an #abstract_class
then both B.base_class and C.base_class would return B as the answer since
A is an abstract_class.