def collection_attributes(*attrs)
      @collection_attributes ||= []
      if attrs.any?
        @collection_attributes.map!(&:to_sym).concat(attrs).uniq!
        @collection_attributes.each { |a| setup_collection(a) }
      end
      @collection_attributes
    end
def collection_attributes(*attrs)
      @collection_attributes ||= []
      if attrs.any?
        @collection_attributes.map!(&:to_sym).concat(attrs).uniq!
        @collection_attributes.each { |a| setup_collection(a) }
      end
      @collection_attributes
    end
For collections that are represented as attributes (i.e. inline, no href)

 @example
     collection_attributes :recipients