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_MDP_L.m
    path of file: ./repos/bspm/thirdparty/spm12/toolbox/DEM
    
    the code of the file until where you have to start completion: function L = spm_MDP_L(P,M,U,Y)
% log-likelihood function
% FORMAT L = spm_mdp_L(P,M,U,Y)
% P    - parameter structure
% M    - generative model
% U    - inputs (observations or stimuli)
% Y    - observed responses (or choices)
%
% This auxiliary function evaluates the log likelihood of a sequence of

    
function L = spm_MDP_L(P,M,U,Y)
% log-likelihood function
% FORMAT L = spm_mdp_L(P,M,U,Y)
% P    - parameter structure
% M    - generative model
% U    - inputs (observations or stimuli)
% Y    - observed responses (or choices)
%
% This auxiliary function evaluates the log likelihood of a sequence of
% choices within and between trials under and MDP model of choice behaviour
% parameterised by P.required fields of the model MR:
%
% M.G   - a function that returns a particular MDP parameterisation; i.e.,
%         MDP = M.G(P);
%__________________________________________________________________________

% place parameters in MDP
%--------------------------------------------------------------------------
if ~isstruct(P); P = spm_unvec(P,M.pE); end