Return True|False if the AMP shoukd be displayed in oneline (one_lineline=true|false).

def one_line(self):
        """Return True|False if the AMP shoukd be displayed in oneline (one_lineline=true|false)."""
        ret = self.get('one_line')
        if ret is None:
            return False
        else:
            return ret.lower().startswith('true')