Return an axis which may need to be initialized from
        a new figure.

def _init_axis(self, fig, axis):
        """
        Return an axis which may need to be initialized from
        a new figure.
        """
        if not fig and self._create_fig:
            fig = plt.figure()
            l, b, r, t = self.fig_bounds
            inches = self.fig_inches
            fig.subplots_adjust(left=l, bottom=b, right=r, top=t)
            fig.patch.set_alpha(self.fig_alpha)
            if isinstance(inches, (tuple, list)):
                inches = list(inches)
                if inches[0] is None:
                    inches[0] = inches[1]
                elif inches[1] is None:
                    inches[1] = inches[0]
                fig.set_size_inches(list(inches))
            else:
                fig.set_size_inches([inches, inches])
            axis = fig.add_subplot(111, projection=self.projection)
            axis.set_aspect('auto')
        return fig, axis