# File lib/rss/atom.rb, line 179
179:       def self.append_features(klass)
180:         super
181:         klass.class_eval do
182:           @content_type = :w3cdtf
183:           include(ContentModel)
184:         end
185:       end

     # File lib/rss/atom.rb, line 187
187:       def atom_validate(ignore_unknown_element, tags, uri)
188:         raise NotAvailableValueError.new(tag_name, "") if content.nil?
189:       end