module ActiveAdmin::ResourceController::ResourceClassMethods

def override_resource_class_methods!

of ActiveAdmin::Resource
methods to only return the class defined in the instance
Override the default `resource_class` class and instance 
def override_resource_class_methods!
  class_exec do
    def self.resource_class=(klass); end
    def self.resource_class
      @active_admin_config ? @active_admin_config.resource_class : nil
    end
    def resource_class
      self.class.resource_class
    end
  end
end