def features
      @features ||= data_entries.collect{|sid,data| data.keys.collect{|id| OpenTox::Feature.find(id)}}.flatten.uniq
      @features
    end
def features
      @features ||= data_entries.collect{|sid,data| data.keys.collect{|id| OpenTox::Feature.find(id)}}.flatten.uniq
      @features
    end
Get all features
 @return [Array<OpenTox::Feature>]