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: demo_HRF.m
    path of file: ./repos/PsPM/src/ext/VBA/subfunctions
    
    the code of the file until where you have to start completion: 
% Demo for Balloon model.
% This demo inverts a balloon model of the HRF.

close all
clear all


% Choose basic settings for simulations
TR = 2e0;                    % sampling time interval (in sec)
n_t = 60/TR;                % number of time samples (over 40 sec)
deltat = 5e-2;              
    
function
g_fname = @g_HRF3;               % Balloon model observation function
disp('Extracting HRF params...')
% try
%     [theta,phi] = get_HRFparams(TR,deltat);
% catch
    theta = [
        0.2629
        0.1514
        -0.6285
        -0.2889
        0
        0.2646
        ];
    phi = [
        0.5770
        -0.5345
        ];
% end