def _to_dict(self):
        """Return a json dictionary representing this model."""
        _dict = {}
        if hasattr(self, 'content') and self.content is not None:
            _dict['content'] = self.content
        if hasattr(self, 'id') and self.id is not None:
            _dict['id'] = self.id
        if hasattr(self, 'created') and self.created is not None:
            _dict['created'] = self.created
        if hasattr(self, 'updated') and self.updated is not None:
            _dict['updated'] = self.updated
        if hasattr(self, 'contenttype') and self.contenttype is not None:
            _dict['contenttype'] = self.contenttype
        if hasattr(self, 'language') and self.language is not None:
            _dict['language'] = self.language
        if hasattr(self, 'parentid') and self.parentid is not None:
            _dict['parentid'] = self.parentid
        if hasattr(self, 'reply') and self.reply is not None:
            _dict['reply'] = self.reply
        if hasattr(self, 'forward') and self.forward is not None:
            _dict['forward'] = self.forward
        return _dict
Return a json dictionary representing this model.