'Set the hold state
The ``hold`` mechanism is deprecated and will be removed in
v3.0.  The behavior will remain consistent with the
long-time default value of True.
If *hold* is *None* (default), toggle the *hold* state.  Else
set the *hold* state to boolean value *b*.
Examples::
# toggle hold
hold()
# turn hold on
hold(True)
# turn hold off
hold(False)
When hold is *True*, subsequent plot commands will be added to
the current axes.  When hold is *False*, the current axes and
figure will be cleared on the next plot command'

@cbook.deprecated(u'2.0', message=_hold_msg)
def hold(self, b=None):

    if (b is None):
        self._hold = (not self._hold)
    else:
        self._hold = b
