code: def parameterize(string, separator='-'):
      
      string = transliterate(string)
      # Turn unwanted chars into the separator
      string = re.sub(r"(?i)[^a-z0-9\-_]+", separator, string)
      if separator:
          re_sep = re.escape(separator)
          # No more than one of the separator in a row.
          string = re.sub(r'%s{2,}' % re_sep, separator, string)
          # Remove leading/trailing separator.
          string = re.sub(r"(?i)^%(sep)s|%(sep)s$" % {'sep': re_sep}, '', string)
  
      return string.lower()
docs: Replace special characters in a string so that it may be used as part of a
      'pretty' URL.
      Example::
          >>> parameterize(u"Donald E. Knuth")
          'donald-e-knuth'