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: RangeBearingSensor.m
    path of file: ./repos/Robotics-Toolbox/rvctools/release10.3.1/robot
    
    the code of the file until where you have to start completion: %RangeBearingSensor Range and bearing sensor class
%
% A concrete subclass of the Sensor class that implements a range and bearing
% angle sensor that provides robot-centric measurements of landmark points in 
% the world. To enable this it holds a references to a map of the world (LandmarkMap object)
% and a robot (Vehicle subclass object) that moves in S
    
function J = Gz(s, xv, z)
            %RangeBearingSensor.Gz Jacobian dg/dz
            %
            % J = S.Gz(X, Z) is the Jacobian dg/dz (2x2) at the vehicle state X (3x1) for
            % sensor observation Z (2x1).
            %
            % See also RangeBearingSensor.g.
            theta = xv(3);
            r = z(1);
            bearing = z(2);
            J = [
                cos(theta + bearing),   -r*sin(theta + bearing);
                sin(theta + bearing),    r*cos(theta + bearing)
                ];
        end