'If *vmin* or *vmax* is not given, they are initialized from the
minimum and maximum value respectively of the first input
processed.  That is, *__call__(A)* calls *autoscale_None(A)*.
If *clip* is *True* and the given value falls outside the range,
the returned value will be 0 or 1, whichever is closer.
Returns 0 if::
vmin==vmax
Works with scalars or arrays, including masked arrays.  If
*clip* is *True*, masked values are set to 1; otherwise they
remain masked.  Clipping silently defeats the purpose of setting
the over, under, and masked colors in the colormap, so it is
likely to lead to surprises; therefore the default is
*clip* = *False*.'

def __init__(self, vmin=None, vmax=None, clip=False):

    self.vmin = vmin
    self.vmax = vmax
    self.clip = clip
