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_dcm_erp_sensitivity.m
    path of file: ./repos/malini/Codes/deconvolution - model/spm8/toolbox/dcm_meeg
    
    the code of the file until where you have to start completion: function x = spm_dcm_erp_sensitivity(DCM,C)
% plots change in source activity with a contrast of parameters
% FORMAT x = spm_dcm_erp_sensitivity(DCM,C)
%
% DCM - DCM structure:
% store estimates in DCM

    
function x = spm_dcm_erp_sensitivity(DCM,C)
% plots change in source activity with a contrast of parameters
% FORMAT x = spm_dcm_erp_sensitivity(DCM,C)
%
% DCM - DCM structure:
% store estimates in DCM
%--------------------------------------------------------------------------
% DCM.M  - model specification
% DCM.xY - data structure
% DCM.xU - input structure
% DCM.Ep - conditional expectation f(x,u,p)
% DCM.Cp - conditional covariances G(g)
% DCM.Eg - conditional expectation
% DCM.Cg - conditional covariances
% DCM.Pp - conditional probability
% DCM.H  - conditional responses (y), projected space
% DCM.K  - conditional responses (x)
% DCM.R  - conditional residuals (y)
% DCM.F  - Laplace log evidence
% DCM.L  - Laplace log evidence components
% DCM.ID - data ID
% 
% 
% DCM.options.h
% DCM.options.Nmodes
% DCM.options.onset
% DCM.options.model
% DCM.options.lock
% DCM.options.symm
%
% C      - contrast (in the form of DCM.pE)
%        - or string identifying a parameter: e.g. 'A{2}(3,1)' 
%
% x{i}   - dx/dC for contributing sources {trial i}
%__________________________________________________________________________
% Copyright (C) 2008 Wellcome Trust Centre for Neuroimaging

% Karl Friston
% $Id: spm_dcm_erp_sensitivity.m 4186 2011-02-01 20:11:32Z karl $

% check options
%==========================================================================

% unpack
%--------------------------------------------------------------------------
xY     = DCM.xY;
xU     = DCM.xU;
M      = DCM.M;

% contrast
%--------------------------------------------------------------------------
if ischar(C)
    Cp = DCM.Ep;
    Cp = spm_unvec(spm_vec(Cp)*0,Cp);
    
    eval(['Cp.' C ' = 1;']);
    C  = Cp;
end