code: def to_utf8(s):
      
      if six.PY2:
          if isinstance(s, str):
              return s
          elif isinstance(s, unicode):
              return s.encode('utf-8')
          elif isinstance(s, (list, tuple, set)):
              return [to_utf8(v) for v in s]
          else:
              return s
      else:
          return s
docs: Convert a string to utf8. If the argument is an iterable
      (list/tuple/set), then each element of it would be converted instead.
  
      >>> to_utf8('a')
      'a'
      >>> to_utf8(u'a')
      'a'
      >>> to_utf8([u'a', u'b', u'\u4f60'])
      ['a', 'b', '\\xe4\\xbd\\xa0']