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: pu2_encode.m
    path of file: ./repos/HDR_Toolbox/source_code/Metrics/util
    
    the code of the file until where you have to start completion: function P = pu2_encode( L )
% Perceptually uniform luminance encoding using the CSF from HDR-VDP-2
%
% P = pu2_encode( L )
%
% Transforms absolute luminance values L into approximately perceptually 
% uniform values P. 
%
% This is meant to be used with display-referred quality metrics - the
% image values much correspond to the l
    
function S = hdrvdp_joint_rod_cone_sens( la, metric_par )
% Copyright (c) 2011, Rafal Mantiuk <mantiuk@gmail.com>

% Permission to use, copy, modify, and/or distribute this software for any
% purpose with or without fee is hereby granted, provided that the above
% copyright notice and this permission notice appear in all copies.
%
% THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
% WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
% MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
% ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
% WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
% ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
% OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

cvi_sens_drop = metric_par.csf_sa(2); % in the paper - p6
cvi_trans_slope = metric_par.csf_sa(3); % in the paper - p7
cvi_low_slope = metric_par.csf_sa(4); % in the paper - p8

S = metric_par.csf_sa(1) * ( (cvi_sens_drop./la).^cvi_trans_slope+1).^-cvi_low_slope;

end