code: def append(self, parent, content):
          
          appender = self.default
          for a in self.appenders:
              if a[0] == content.value:
                  appender = a[1]
                  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}