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: m_07_gr4j_4p_2s.m
    path of file: ./repos/MARRMoT/MARRMoT/Models/Model files
    
    the code of the file until where you have to start completion: classdef m_07_gr4j_4p_2s < MARRMoT_model
% Class for hydrologic conceptual model: GR4J

% Copyright (C) 2019, 2021 Wouter J.M. Knoben, Luca Trotter
% This file is part of the Modular Assessment of Rainfall-Runoff Models
% Toolbox (MARRMoT).
% MARRMoT is a free software (GNU GPL v3) and distributed WITHOUT ANY
% WARRANTY. See <https://www.gnu.org/licenses/> for details.

% Model references
% Perrin, C., Michel, C., & Andréassian, V. (2003). Improvement of a 
% parsimonious model for streamflow simulation. Journal of Hydrology, 
% 279(1-4), 275–289. http://doi.org/10.1016/S0022-1694(03)00225-7
%
% Santos, L., Thirel, G., & Perrin, C. (2017). State-space representation 
% of a bucket-type rainfall-runoff model: a case study with State-Space GR4
% (version 1.0). Geoscientific Model Development Discussions, 1–22. 
% http://doi.org/10.5194/gmd-2017-264

    properties
        % model-specific attributes
    end
    methods
        
        % creator method
        function obj = m_07_gr4j_4p_2s()            
            obj.numStores = 2;                                             % number of model stores
            obj.numFluxes = 13;                                            % number of model fluxes
            obj.numParams = 4;
            
            obj.JacobPattern  = [1,1;
                                 1,1];                                     % Jacobian matrix of model store ODEs
                             
            
    
function [dS, fluxes] = model_fun(obj, S)
            % parameters
            theta   = obj.theta;
            x1      = theta(1);     % Maximum soil moisture storage [mm]
            x2      = theta(2);     % Water exchange coefficient [mm/d]
            x3      = theta(3);     % Maximum routing store storage [mm]
            x4      = theta(4);     % Flow delay [d]
            
            % delta_t
            delta_t = obj.delta_t;
            
            % unit hydrographs and still-to-flow vectors
            uhs = obj.uhs;
            uh_q9 = uhs{1};
            uh_q1 = uhs{2};
            
            % stores
            S1 = S(1);
            S2 = S(2);
            
            % climate input
            t = obj.t;                             % this time step
            climate_in = obj.input_climate(t,:);   % climate at this step
            P  = climate_in(1);
            Ep = climate_in(2);
            T  = climate_in(3);
            
            % fluxes functions
            flux_pn   = max(P-Ep,0);
            flux_en   = max(Ep-P,0);
            flux_ef   = P - flux_pn;
            flux_ps   = saturation_4(S1,x1,flux_pn);
            flux_es   = evap_11(S1,x1,flux_en);
            flux_perc = percolation_3(S1,x1);
            flux_q9   = route(.9.*(flux_pn - flux_ps + flux_perc), uh_q9);
            flux_q1   = route(.1.*(flux_pn - flux_ps + flux_perc), uh_q1);
            flux_fr   = recharge_2(3.5,S2,x3,x2);
            flux_fq   = flux_fr;
            flux_qr   = baseflow_3(S2,x3);
            flux_qt   = flux_qr + max(flux_q1 + flux_fq,0);
            % this flux is not included in original MARRMoT,
            % but it is useful to calculate the water balance
            flux_ex = flux_fr + max(flux_q1 + flux_fq,0) - flux_q1;      

            % stores ODEs
            dS1 = flux_ps - flux_es - flux_perc;
            dS2 = flux_q9 + flux_fr - flux_qr;
            
            % outputs
            dS = [dS1 dS2];
            fluxes = [flux_pn,   flux_en, flux_ef, flux_ps, flux_es,...
                      flux_perc, flux_q9, flux_q1, flux_fr, flux_fq,...
                      flux_qr,   flux_qt, flux_ex];
        end