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: GradientBoostingRegressor.m
    path of file: ./repos/sklearn-matlab/lib/ensemble
    
    the code of the file until where you have to start completion: classdef GradientBoostingRegressor < BaseEstimator & RegressorMixin
    % Gra
    
function to be optimized. 'ls' refers to least squares
        % regression.
        loss = 'ls';
        
        n_estimators = 100; % The number of boosting stages to perform.
    end
    
    properties (GetAccess = 'public', SetAccess = 'private')
        % attributes
        regressor; % Matlab ensemble object
    end
    
    methods
        % constructor
        function obj = GradientBoostingRegressor(params)
            if nargin>0
                obj.set_params(params)
            end