def _render_attributes(self,used_fields,nsmap):
        for f in self._fields:
            val = getattr(self,f.field_name)
            datas = iter(f.render_attributes(self,val,nsmap))
            try:
                data = datas.next()
            except __HOLE__:
                pass
            else:
                used_fields.add(f)
                yield data
                for data in datas:
                    yield data
dataset/ETHPy150Open rfk/dexml/dexml/__init__.py/Model._render_attributes