def build(self, builder):
        """
        Build XML by appending to builder
        """
        if self.text is None:
            raise ValueError("Text is not set.")
        params = {}
        if self.sponsor_or_site is not None:
            params['SponsorOrSite'] = self.sponsor_or_site

        builder.start("Comment", params)
        builder.data(self.text)
        builder.end("Comment")