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: spm_gx_hdm.m
    path of file: ./repos/malini/Codes/deconvolution - model/spm8
    
    the code of the file until where you have to start completion: function [y] = spm_gx_hdm(x,u,P,M)
% Simulated BOLD response to input.
% FORMAT [y] = spm_gx_hdm(x,u,P,M)
% y    - BOLD response (%)
% x    - state vector     (see spm_fx_dcm)
% P    - Parameter vector (see spm_fx_dcm)
%__________________________________________________________________________
%
% This function implements the BOLD signal model described in: 
%
% Stephan KE, Weiskopf N, Drysdale PM, Robinson PA, Friston KJ (2007)
% Comparing hemodynamic models with DCM. NeuroImage 38: 387-401.
%__________________________________________________________________________
% Copyright (C) 2008 Wellcome Trust Centre for Neuroimaging

    
function [y] = spm_gx_hdm(x,u,P,M)
% Simulated BOLD response to input.
% FORMAT [y] = spm_gx_hdm(x,u,P,M)
% y    - BOLD response (%)
% x    - state vector     (see spm_fx_dcm)
% P    - Parameter vector (see spm_fx_dcm)
%__________________________________________________________________________
%
% This function implements the BOLD signal model described in: 
%
% Stephan KE, Weiskopf N, Drysdale PM, Robinson PA, Friston KJ (2007)
% Comparing hemodynamic models with DCM. NeuroImage 38: 387-401.
%__________________________________________________________________________
% Copyright (C) 2008 Wellcome Trust Centre for Neuroimaging
 
% Karl Friston & Klaas Enno Stephan
% $Id: spm_gx_hdm.m 3812 2010-04-07 16:52:05Z karl $


% biophysical constants for 1.5 T: 
%==========================================================================

% echo time (seconds)
%--------------------------------------------------------------------------
try
    TE = M(1).TE;
catch
    TE = 0.04;
end