code: def clean_response_type(self):
          
          response_type = self.cleaned_data.get('response_type')
  
          if not response_type:
              raise OAuthValidationError({'error': 'invalid_request',
                  'error_description': "No 'response_type' supplied."})
  
          types = response_type.split(" ")
  
          for type in types:
              if type not in RESPONSE_TYPE_CHOICES:
                  raise OAuthValidationError({
                      'error': 'unsupported_response_type',
                      'error_description': u"'%s' is not a supported response "
                          "type." % type})
  
          return response_type
docs: :rfc:`3.1.1` Lists of values are space delimited.