def __missing__(self, key):
        if self.default_factory is None:
            raise KeyError(key)
        else:
            ret = self[key] = self.default_factory(name=key)
            return ret
def __init__(self, data, amount_clusters, means=None, variances=None, observer=None, tolerance=0.00001, iterations=100):
        """!
        @brief Initializes Expectation-Maximization algorithm for cluster analysis.