'Construct a spline object from given tck'

@classmethod
def _from_tck(cls, tck, ext=0):

    self = cls.__new__(cls)
    (t, c, k) = tck
    self._eval_args = tck
    self._data = (None, None, None, None, None, k, None, len(t), t, c, None, None, None, None)
    self.ext = ext
    return self
