def clean_response_type(self):
        """
        :rfc:`3.1.1` Lists of values are space delimited.
        """
        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
:rfc:`3.1.1` Lists of values are space delimited.