def __init__(self, wvd, shape, scale):
    ' `wvd` may be either a dict or list of whiskers '
    object.__init__(self)
    self._map = {}
    self._shape = shape
    self._scale = scale
    self._stride = stride = (shape[1] / scale)
    self.topx = (lambda p: (int((p[0] / scale)) + (stride * int((p[1] / scale)))))
    self._build_inverse_table(wvd)
`wvd` may be either a dict or list of whiskers
def __init__(self, wvd, shape, scale):
    '  '
    object.__init__(self)
    self._map = {}
    self._shape = shape
    self._scale = scale
    self._stride = stride = (shape[1] / scale)
    self.topx = (lambda p: (int((p[0] / scale)) + (stride * int((p[1] / scale)))))
    self._build_inverse_table(wvd)