'Use the cross-validation estimate to create a probability
distribution for the experiment used to generate
``freqdists``.
:type freqdists: list(FreqDist)
:param freqdists: A list of the frequency distributions
generated by the experiment.
:type bins: int
:param bins: The number of sample values that can be generated
by the experiment that is described by the probability
distribution.  This value must be correctly set for the
probabilities of the sample values to sum to one.  If
``bins`` is not specified, it defaults to ``freqdist.B()``.'

def __init__(self, freqdists, bins):

    self._freqdists = freqdists
    self._heldout_probdists = []
    for fdist1 in freqdists:
        for fdist2 in freqdists:
            if (fdist1 is not fdist2):
                probdist = HeldoutProbDist(fdist1, fdist2, bins)
                self._heldout_probdists.append(probdist)
