docs: def addTitle(self, title, titleAlignments):
          """
          Add a new title to self.
  
          @param title: A C{str} title.
          @param titleAlignments: An instance of L{TitleAlignments}.
          @raises KeyError: If the title is already present.
          """
          if title in self:
              raise KeyError('Title %r already present in TitlesAlignments '
                             'instance.' % title)
          else:
              self[title] = titleAlignments