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: dwl.m
    path of file: ./repos/Image-Harmonization-Dataset-iHarmony4/Xue et al/dependency/optprop/framework
    
    the code of the file until where you have to start completion: function z=dwl(varargin)
%DWL Return or set the session default wavelength range.
%   Z=DWL assigns the default wavelength range to Z. DWL is purly a
%   convenience funtion and be replaced by optgetprop('WLRange').

    
function z=dwl(varargin)
%DWL Return or set the session default wavelength range.
%   Z=DWL assigns the default wavelength range to Z. DWL is purly a
%   convenience funtion and be replaced by optgetprop('WLRange').
%
%   See also: OPTGETPREF

% Part of the OptProp toolbox, $Version: 2.1 $
% Author:  Jerker Wågberg, More Research & DPC, Sweden
% Email: ['jerker.wagberg' char(64) 'more.se']

% $Id: dwl.m 23 2007-01-28 22:55:34Z jerkerw $
	if nargin==0
		z=optgetpref('WLRange');
	else
		optsetpref('WLRange', varargin{:});
		end