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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def plot(self, ax=None, legend=None, return_fig=False, **kwargs):
 """ Plot a curve. Args: ax (ax):
 A matplotlib axis. legend (striplog.legend):
 A legend. Optional. return_fig (bool):
 whether to return the matplotlib figure. Default False. kwargs: Arguments for ``ax.set()`` Returns: ax. If you passed in an ax, otherwise None. """

        if ax is None:
            fig = plt.figure(figsize=(2, 10))
            ax = fig.add_subplot(111)
            return_ax = False
        else:
            return_ax = True

        d = None
        if legend is not None:
            try:
                d = legend.get_decor(self)
            except:
                pass

        if d is not None:
            kwargs['color'] = d.colour
            kwargs['lw'] = getattr(d, 'lineweight', None) or getattr(d, 'lw', 1)
            kwargs['ls'] = getattr(d, 'linestyle', None) or getattr(d, 'ls', '-')

            # Attempt to get axis parameters from decor.
            axkwargs = {}

            xlim = getattr(d, 'xlim', None)
            if xlim is not None:
                axkwargs['xlim'] = list(map(float, xlim.split(',')))

            xticks = getattr(d, 'xticks', None)
            if xticks is not None:
                axkwargs['xticks'] = list(map(float, xticks.split(',')))

            xscale = getattr(d, 'xscale', None)
            if xscale is not None:
                axkwargs['xscale'] = xscale

            ax.set(**axkwargs)

        ax.plot(self, self.basis, **kwargs)
        ax.set_title(self.mnemonic)  # no longer needed
        ax.set_xlabel(self.units)

        if False:  # labeltop of axes?
            ax.xaxis.tick_top()

        if True:  # rotate x-tick labels
            labels = ax.get_xticklabels()
            for label in labels:
                label.set_rotation(90)

        ax.set_ylim([self.stop, self.start])
        ax.grid('on', color='k', alpha=0.33, lw=0.33, linestyle='-')

        if return_ax:
            return ax
        elif return_fig:
            return fig
        else:
            return None