Get if sound mode is supported from device.

        Method queries device via HTTP.
        Returns "True" if sound mode supported and "False" if not.
        This method is for pre 2016 AVR(-X) devices

def _get_support_sound_mode_avr(self):
        """
        Get if sound mode is supported from device.

        Method queries device via HTTP.
        Returns "True" if sound mode supported and "False" if not.
        This method is for pre 2016 AVR(-X) devices
        """
        # Set sound mode tags to be checked if available
        relevant_tags = {"selectSurround": None, "SurrMode": None}

        # Get status XML from Denon receiver via HTTP
        try:
            root = self.get_status_xml(self._urls.status)
        except (ValueError, requests.exceptions.RequestException):
            pass
        else:
            # Process the tags from this XML
            relevant_tags = self._get_status_from_xml_tags(root, relevant_tags)

        # Second option to update variables from different source
        if relevant_tags:
            try:
                root = self.get_status_xml(self._urls.mainzone)
            except (ValueError,
                    requests.exceptions.RequestException):
                pass
            else:
                # Get the tags from this XML
                relevant_tags = self._get_status_from_xml_tags(root,
                                                               relevant_tags)

        # if sound mode not found in the status XML, return False
        if relevant_tags:
            self._support_sound_mode = False
            return False
        # if sound mode found, the relevant_tags are empty: return True.
        self._support_sound_mode = True
        return True