sci_patch.rb

module MongoMapper
  module Plugins
    module Sci
      module ClassMethods
        def inherited(subclass)
          super
          if @collection_name == subclass.instance_variable_get("@collection_name")
            key :_type, String unless key?(:_type)
            subclass.single_collection_parent = self
            subclass.instance_variable_set("@single_collection_inherited", true)
          end
        end
      end
    end
  end
end