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: contours_hierarchy_demo.m
    path of file: ./repos/mexopencv/samples
    
    the code of the file until where you have to start completion: %% Contours in OpenCV
%
% In the sample, we will:
%
% * Understand what contours are.
% * Learn about the h
    
function is used. It can also be
% used to draw any shape provided you have its boundary points. Its first
% argument is source image, second argument is the contours which should be
% passed as a cell array, third argument is index of contours (useful when
% drawing individual contour, or -1 to draw all contours). Remaining arguments
% are color, thickness, etc.
%
% Let's see how to find and draw contours of a binary image:
%
%   img = imread('image.jpg')
%   gray = cv.cvtColor(img, 'RGB2GRAY');
%   bw = cv.threshold(gray, 'Otsu');
%   [contours,hierarchy] = cv.findContours(bw, 'Mode','Tree', 'Method','Simple');
%   img = cv.drawContours(img, contours, 'Hierarchy',hierarchy, 'Color',[0 255 0]);
%

%% Contour Approximation Method
%
% This is the third argument in |cv.findContours| function. What does it
% denote actually?
%
% We previously explained that contours are the boundaries of a shape with the
% same intensity. It stores the (x,y) coordinates of the boundary of a shape.
% But does it store all the coordinates? That is specified by this contour
% approximation method.
%
% If you set |Method = None|, all the boundary points are stored. But actually
% do we need all the points? For example, you found the contour of a straight
% line. Do you need all the points on the line to represent that line? No, we
% need just two end