when defined?(ActiveRecord::Base)            && ancestors.include?(ActiveRecord::Base),
               defined?(Mongoid::Document)             && ancestors.include?(Mongoid::Document),
               defined?(MongoMapper::Document)         && ancestors.include?(MongoMapper::Document),
               defined?(MongoMapper::EmbeddedDocument) && ancestors.include?(MongoMapper::EmbeddedDocument)
            before_destroy :remove_from_recommendable!