Output an iframe containing the plot in the notebook without saving.

def plot(self,
             data,
             chart_type,
             chart_package='corechart',
             options=None,
             w=800,
             h=420):
        """Output an iframe containing the plot in the notebook without saving."""
        return HTML(
            self.iframe.format(
                source=self.render(
                    data=data,
                    options=options,
                    chart_type=chart_type,
                    chart_package=chart_package,
                    head=self.head),
                w=w,
                h=h))