'Update the current values.  If any kwarg is None, default to
the current value, if set, otherwise to rc'

def update(self, left=None, bottom=None, right=None, top=None, wspace=None, hspace=None):

    thisleft = getattr(self, u'left', None)
    thisright = getattr(self, u'right', None)
    thistop = getattr(self, u'top', None)
    thisbottom = getattr(self, u'bottom', None)
    thiswspace = getattr(self, u'wspace', None)
    thishspace = getattr(self, u'hspace', None)
    self._update_this(u'left', left)
    self._update_this(u'right', right)
    self._update_this(u'bottom', bottom)
    self._update_this(u'top', top)
    self._update_this(u'wspace', wspace)
    self._update_this(u'hspace', hspace)
    def reset():
        self.left = thisleft
        self.right = thisright
        self.top = thistop
        self.bottom = thisbottom
        self.wspace = thiswspace
        self.hspace = thishspace
    if self.validate:
        if (self.left >= self.right):
            reset()
            raise ValueError(u'left    cannot    be    >=    right')
        if (self.bottom >= self.top):
            reset()
            raise ValueError(u'bottom    cannot    be    >=    top')
