You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: SE2UKF.m
    path of file: ./repos/libDirectional/lib/filters
    
    the code of the file until where you have to start completion: classdef SE2UKF < AbstractSE2Filter
    % Applies UKF to dual-quaternion-based Estimation on SE(2).
    %
    % A Stochastic Filter for Planar Rigid-Body Motions,
    % Igor Gilitschenski, Gerhard Kurz, and Uwe D. Hanebeck,
    % Proceedings of the 2015 IEEE International Conference on Multisensor
    % Fusion and Integration for Intelligent Systems (MFI),
    % San Diego, USA, 2015
    
    properties (Access = public)
        gauss % Current state 
    
function this = updateIdentity(this, gaussMeas, z)
            % Incorporates measurement into current estimate.
            %
            %  Parameters:
            %    z - Measurement given as a 4d dual quaternion restricted to
            %        SE(2)
            
            assert(all(size(gaussMeas.C)==[4 4]), 'Observation covariance matrix has wrong size');
            assert(all(size(gaussMeas.mu)==[4,1]), 'mu must be 4d column vector.');
            assert(norm(gaussMeas.mu(1:2))==1, 'First two entries of the mean of the observation noise must be normalized');
            
            % Take closer quaternion to improve estimate.
            if (norm(z-this.gauss.mu)>norm(-z-this.gauss.mu))
                z = -z;
            end