code: def replace_tags(string, from_tag='i', to_tag='italic'):
      
      string = string.replace('<' + from_tag + '>', '<' + to_tag + '>')
      string = string.replace('</' + from_tag + '>', '</' + to_tag + '>')
      return string
docs: Replace tags such as <i> to <italic>
      <sup> and <sub> are allowed and do not need to be replaced
      This does not validate markup