code: def force_unicode(string, encoding='utf-8', strings_only=False, errors='strict'):
      
      # Handle the common case first, saves 30-40% in performance when s
      # is an instance of unicode. This function gets called often in that
      # setting.
      if isinstance(string, str):
          return string
      if strings_only and is_protected_type(string):
          return string
      try:
          if not isinstance(string, str):
              if hasattr(string, '__unicode__'):
                  string = string.__unicode__()
              else:
                  try:
                      string = str(string, encoding, errors)
                  except UnicodeEncodeError:
                      if not isinstance(string, Exception):
                          raise
                      # If we get to here, the caller has passed in an Exception
                      # subclass populated with non-ASCII data without special
                      # handling to display as a string. We need to handle this
                      # without raising a further exception. We do an
                      # approximation to what the Exception's standard str()
                      # output should be.
                      string = ' '.join([force_unicode(arg, encoding,
                                                       strings_only,
                                                       errors) for arg in string])
          elif not isinstance(string, str):
              # Note: We use .decode() here, instead of unicode(s, encoding,
              # errors), so that if s is a SafeString, it ends up being a
              # SafeUnicode at the end.
              string = string.decode(encoding, errors)
      except UnicodeDecodeError as ex:
          if not isinstance(string, Exception):
              raise DjangoUnicodeDecodeError(string, *ex.args)
          else:
              # If we get to here, the caller has passed in an Exception
              # subclass populated with non-ASCII bytestring data without a
              # working unicode method. Try to handle this without raising a
              # further exception by individually forcing the exception args
              # to unicode.
              string = ' '.join([force_unicode(arg, encoding, strings_only,
                                               errors) for arg in string])
      return string
docs: Similar to smart_unicode, except that lazy instances are resolved to
      strings, rather than kept as lazy objects.
  
      If strings_only is True, don't convert (some) non-string-like objects.