code: def parse_title(self, docname):
          
          env = self.document.settings.env
          title = self.titles.get(docname)
          if title is None:
              fname = os.path.join(env.srcdir, docname+'.rst')
              try:
                  f = open(fname, 'r')
              except IOError:
                  title = False
              else:
                  for line in f:
                      if len(line) > 0 and (line[0].isalnum() or line[0] == '<'):
                          title = line.rstrip()
                          break
                  f.close()
                  if title is None:
                      title = os.path.basename(docname)
              self.titles[docname] = title
          return title
docs: Parse a document title as the first line starting in [A-Za-z0-9<]
             or fall back to the document basename if no such line exists.
             The cmake --help-*-list commands also depend on this convention.
             Return the title or False if the document file does not exist.