How to use the sidekit.mixture.Mixture function in SIDEKIT

:param ubm: a Mixture object used to compute the denominator 
        of the likelihood ratios
    :param enroll: a StatServer object which stat1 attribute contains mean 
        super-vectors of the GMMs to use to compute the numerator of the 
        likelihood ratios.
    :param ndx: an Ndx object which define the list of trials to compute
    :param feature_server: sidekit.FeaturesServer used to load the acoustic parameters
    :param score_mat: a ndarray of scores to fill
    :param seg_idx: the list of unique test segments to process.
        Those test segments should belong to the list of test segments 
        in the ndx object. By setting seg_idx=None, all test segments
        from the ndx object will be processed
    
    """
    assert isinstance(ubm, Mixture), 'First parameter should be a Mixture'
    assert isinstance(enroll, StatServer), 'Second parameter should be a StatServer'
    assert isinstance(ndx, Ndx), 'Third parameter should be a Ndx'
    assert isinstance(feature_server, FeaturesServer), 'Fourth parameter should be a FeatureServer'
    
    if seg_idx is None:
        seg_idx = range(ndx.segset.shape[0])

    for ts in seg_idx:
        logging.info('Compute trials involving test segment %d/%d', ts + 1, ndx.segset.shape[0])

        # Select the models to test with the current segment
        models = ndx.modelset[ndx.trialmask[:, ts]]
        ind_dict = dict((k, i) for i, k in enumerate(ndx.modelset))
        inter = set(ind_dict.keys()).intersection(models)
        idx_ndx = [ind_dict[x] for x in inter]
        ind_dict = dict((k, i) for i, k in enumerate(enroll.modelset))

Gaussian Mixture Models (GMMs) which only mean vectors differ 
    from the UBM.
    
    :param ubm: a Mixture object used to compute the denominator of the 
        likelihood ratios
    :param enroll: a StatServer object which stat1 attribute contains 
        mean super-vectors of the GMMs to use to compute the numerator 
        of the likelihood ratios.
    :param ndx: an Ndx object which define the list of trials to compute
    :param feature_server: a FeatureServer object to load the features
    :param num_thread: number of thread to launch in parallel
    
    :return: a Score object.
    
    """
    assert isinstance(ubm, Mixture), 'First parameter should be a Mixture'
    assert isinstance(enroll, StatServer), 'Second parameter should be a StatServer'
    assert isinstance(ndx, Ndx), 'Third parameter should be a Ndx'
    assert isinstance(feature_server, FeaturesServer), 'Fourth parameter should be a FeatureServer'

    # Remove missing models and test segments
    if feature_server.features_extractor is None:
        existing_test_seg, test_seg_idx = sidekit.sv_utils.check_file_list(ndx.segset,
                                                                           feature_server.feature_filename_structure)
        clean_ndx = ndx.filter(enroll.modelset, existing_test_seg, True)
    elif feature_server.features_extractor.audio_filename_structure is not None:
        existing_test_seg, test_seg_idx = \
            sidekit.sv_utils.check_file_list(ndx.segset, feature_server.features_extractor.audio_filename_structure)
        clean_ndx = ndx.filter(enroll.modelset, existing_test_seg, True)
    else:
        clean_ndx = ndx

prefix='',
                         batch_size=300,
                         uncertainty=False,
                         num_thread=1):
        """
        Parallel extraction of i-vectors using multiprocessing module

        :param ubm: Mixture object (the UBM)
        :param stat_server_filename: name of the file from which the input StatServer is read
        :param prefix: prefix used to store the StatServer in its file
        :param batch_size: number of sessions to process in a batch
        :param uncertainty: a boolean, if True, return the diagonal of the uncertainty matrices
        :param num_thread: number of process to run in parallel
        :return: a StatServer with i-vectors in the stat1 attribute and a matrix of uncertainty matrices (optional)
        """
        assert (isinstance(ubm, Mixture) and ubm.validate()), "Second argument must be a proper Mixture"

        tv_rank = self.F.shape[1]

        # Set useful variables
        with h5py.File(stat_server_filename, 'r') as fh:  # open the first statserver to get size
            _, sv_size = fh[prefix + 'stat1'].shape
            nb_sessions = fh[prefix + "modelset"].shape[0]

            iv_server = StatServer()
            iv_server.modelset = fh.get(prefix + 'modelset').value
            iv_server.segset = fh.get(prefix + 'segset').value

            tmpstart = fh.get(prefix+"start").value
            tmpstop = fh.get(prefix+"stop").value
            iv_server.start = numpy.empty(fh[prefix+"start"].shape, '|O')
            iv_server.stop = numpy.empty(fh[prefix+"stop"].shape, '|O')

This method is provided for didactic purpose and should not be used as it uses 
        to much memory and is to slow. If you want to use a single process
        run: "total_variability_single"

        :param stat_server: the StatServer containing data to train the model
        :param ubm: a Mixture object
        :param tv_rank: rank of the total variability model
        :param nb_iter: number of EM iteration
        :param min_div: boolean, if True, apply minimum divergence re-estimation
        :param tv_init: initial matrix to start the EM iterations with
        :param save_init: boolean, if True, save the initial matrix
        :param output_file_name: name of the file where to save the matrix
        """
        assert(isinstance(stat_server, StatServer) and stat_server.validate()), \
            "First argument must be a proper StatServer"
        assert(isinstance(ubm, Mixture) and ubm.validate()), "Second argument must be a proper Mixture"
        assert(isinstance(tv_rank, int) and (0 < tv_rank <= min(stat_server.stat1.shape))), \
            "tv_rank must be a positive integer less than the dimension of the statistics"
        assert(isinstance(nb_iter, int) and (0 < nb_iter)), "nb_iter must be a positive integer"
 
        gmm_covariance = "diag" if ubm.invcov.ndim == 2 else "full" 

        # Set useful variables
        nb_sessions, sv_size = stat_server.stat1.shape
        feature_size = ubm.mu.shape[1]
        nb_distrib = ubm.w.shape[0]    

        # Whiten the statistics for diagonal or full models
        if gmm_covariance == "diag":
            stat_server.whiten_stat1(ubm.get_mean_super_vector(), 1. / ubm.get_invcov_super_vector())
        elif gmm_covariance == "full":
            stat_server.whiten_stat1(ubm.get_mean_super_vector(), ubm.invchol)