docs: def get_filename(self, tag):
          '''Extract and return a documentation filename from a tag.
  
          Override as necessary, though this default implementation probably
          covers all the cases of interest.
  
          Args:
              tag: A BeautifulSoup Tag that satisfies match_criterion.
  
          Returns:
              A string that would be appropriate to use as the documentation
              filename for an entry in a Zeal database.
          '''
          if tag.find('filename', recursive=False) is not None:
              return tag.filename.contents[0]
          elif tag.find('anchorfile', recursive=False) is not None:
              return tag.anchorfile.contents[0] + '#' + tag.anchor.contents[0]