code: def append(self, parent, content):
          
          appender = self.default
          for matcher, candidate_appender in self.appenders:
              if matcher == content.value:
                  appender = candidate_appender
                  break
          appender.append(parent, content)
docs: Select an appender and append the content to parent.
          @param parent: A parent node.
          @type parent: L{Element}
          @param content: The content to append.
          @type content: L{Content}