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: fill.m
    path of file: ./repos/bspm/thirdparty/spm12/toolbox/marsbar-0.44/@mardo_2
    
    the code of the file until where you have to start completion: function D = fill(D, actions)
% fills missing entries from SPM FMRI design matrix 
% FORMAT D = fill(D, actions)

    
function D = fill(D, actions)
% fills missing entries from SPM FMRI design matrix 
% FORMAT D = fill(D, actions)
% 
% D          - mardo object containing spm design
% actions    - string or cell array of strings with actions:
%            'defaults' - fills empty parts of design with defaults
%            (in fact this is always done)
%            'filter'  - asks for and fills filter
%            'autocorr' - asks for and fills autocorrelation 
%            'for_estimation' fill filter &| autocorr if not present
%            'images'  - asks for and fills with images, mask, scaling
%
% Returns
% D         - returned mardo SPM design
%
% Copied/pasted then rearranged from SPM2 spm_fmri_spm_ui
% Matthew Brett - 17/11/01 - MRS2TH
%
% $Id$

if nargin < 2
  actions = '';
end