docs: def NCBISequenceLink(title, default=None):
      """
      Given a sequence title, like "gi|42768646|gb|AY516849.1| Homo sapiens",
      return an HTML A tag dispalying a link to the info page at NCBI.
  
      title: the sequence title to produce an HTML link for.
      default: the value to return if the title cannot be parsed.
      """
      url = NCBISequenceLinkURL(title)
      if url is None:
          return default
      else:
          return '<a href="%s" target="_blank">%s</a>' % (url, title)