<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def render(self, data, accepted_media_type=None, renderer_context=None):
 """ Renders `data` into serialized XML. """

        if data is None:
            return ''

        stream = StringIO()

        xml = SimplerXMLGenerator(stream, self.charset)
        xml.startDocument()
        xml.startElement(self.root_tag_name, {})

        self._to_xml(xml, data)

        xml.endElement(self.root_tag_name)
        xml.endDocument()
        return stream.getvalue()