polymorphic_inverse_of

# File activerecord/lib/active_record/reflection.rb, line 686
      def polymorphic_inverse_of(associated_class)
        if has_inverse?
          if inverse_relationship = associated_class._reflect_on_association(options[:inverse_of])
            inverse_relationship
          else
            raise InverseOfAssociationNotFoundError.new(self, associated_class)
          end
        end
      end