def sum_forward_edge_accuracy(forward_edge):
    """Add up all probabilities from a forward edge"""
    sum_prob = 0

    def get_probability_info(forward_edge):
        """Get event information from maximum_expected_accuracy_alignment"""
        nonlocal sum_prob
        sum_prob = sum_prob + forward_edge[2]
        if forward_edge[4] is not None:
            get_probability_info(forward_edge[4])
        else:
            pass

    get_probability_info(forward_edge)

    return sum_prob