cdf: 'FDRV' object has no attribute 'xs'

[pelegm]

The following:

In [4]: ps = drv.pspace.FDPSpace([1] * 8 + [0] + [1]*2 + [0])

In [5]: d = drv.rv.FDRV('d', ps, lambda x: x**2)

In [6]: d.cdf(0)

raises

Traceback (most recent call last):
  File "<ipython-input-6-66ba4bb58e45>", line 1, in <module>
    d.cdf(0)
  File "drv/rv.py", line 151, in cdf
    return self._cdf(self.xs.index(k))
AttributeError: 'FDRV' object has no attribute 'xs'