'set the norm limits for image scaling; if *vmin* is a length2
sequence, interpret it as ``(vmin, vmax)`` which is used to
support setp
ACCEPTS: a length 2 sequence of floats'

def set_clim(self, vmin=None, vmax=None):

    if (vmax is None):
        try:
            (vmin, vmax) = vmin
        except (TypeError, ValueError):
            pass
    if (vmin is not None):
        self.norm.vmin = vmin
    if (vmax is not None):
        self.norm.vmax = vmax
    self.changed()
