'Close the axes object and clean up.
Bars from bar charts are given to PlotlyRenderer one-by-one,
thus they need to be taken care of at the close of each axes object.
The self.current_bars variable should be empty unless a bar
chart has been created.
Positional arguments:
ax -- an mpl axes object, not required at this time.'

def close_axes(self, ax):

    self.draw_bars(self.current_bars)
    self.msg += '        Closing    axes\n'
    self.x_is_mpl_date = False
