'Data should be keyed by doc-id, values should be iterable'

def initialize(self, data):

    self._alpha_sum = (self._alpha * self._K)
    self._state = defaultdict(dict)
    self._vocab = set([])
    for dd in data:
        for ww in xrange(len(data[dd])):
            self._vocab.add(data[dd][ww])
            self._state[dd][ww] = (-1)
    self._W = len(self._vocab)
    self._lambda_sum = (float(self._W) * self._lambda)
    self._data = data
    print ('Initialized    vocab    of    size    %i' % len(self._vocab))
