          (or UTF-8 bytestrings). The SafeMIMEText class will handle any
          necessary encoding conversions.
          """
          if to:
              if isinstance(to, six.string_types):
                  raise TypeError('"to" argument must be a list or tuple')
              self.to = list(to)
          else:
              self.to = []
          if cc:
 
</s> remove             if isinstance(cc, six.string_types):
 </s> add             if isinstance(cc, str): </s> remove             if isinstance(bcc, six.string_types):
 </s> add             if isinstance(bcc, str): </s> remove             if isinstance(reply_to, six.string_types):
 </s> add             if isinstance(reply_to, str): </s> remove         if isinstance(ds_input, six.string_types):
 </s> add         if isinstance(ds_input, str): </s> remove     if not isinstance(lookup_view, six.string_types):
 </s> add     if not isinstance(lookup_view, str):
            if isinstance(to, str):
          (or UTF-8 bytestrings). The SafeMIMEText class will handle any
          necessary encoding conversions.
          """
          if to:
            if isinstance(to, str):
                  raise TypeError('"to" argument must be a list or tuple')
              self.to = list(to)
          else:
              self.to = []
          if cc:
keep keep keep keep replace keep keep keep keep keep
 Refs #23919 -- Removed six.<various>_types usage

Thanks Tim Graham and Simon Charette for the reviews. 
django/core/mail/message.py