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: perform_curve_extraction.m
    path of file: ./repos/gptoolbox/external/toolbox_fast_marching/toolbox
    
    the code of the file until where you have to start completion: function c_list = perform_curve_extraction(M, t, options)

% perform_curve_extraction - extract level set curves from an image.

    
function c_list = perform_curve_extraction(M, t, options)

% perform_curve_extraction - extract level set curves from an image.
%
%   c_list = perform_curve_extraction(M, t, options)
%
%   'M' is the image.
%   't' is the level.
%   'c_list' is a cell array of 2D curves.
%   'options' is an optional structure with fields: 
%       'max_nb' is the number of curves extracted (only the 'nb' longest).
%       'min_length' is the minimum length (in *pixels*) of extracted curves.
%
%   The image is always assumed to lie in [0,1]x[0,(ny-1)/(nx-1)]
%   where [nx,ny] = size(M).
%
%   Copyright (c) 2004 Gabriel Peyré

if nargin<2
    t = 0;
end