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_conv.m
    path of file: ./repos/bspm/thirdparty/spm12
    
    the code of the file until where you have to start completion: function [X] = spm_conv(X,sx,sy)
% Gaussian convolution
% FORMAT [X] = spm_conv(X,sx[,sy])
% X    - matrix
% sx   - kernel width (FWHM) in pixels
% sy   - optional non-isomorphic smoothing
%__________________________________________________________________________
%
% spm_conv is a one or two dimensional convolution of a matrix variable

    
function [X] = spm_conv(X,sx,sy)
% Gaussian convolution
% FORMAT [X] = spm_conv(X,sx[,sy])
% X    - matrix
% sx   - kernel width (FWHM) in pixels
% sy   - optional non-isomorphic smoothing
%__________________________________________________________________________
%
% spm_conv is a one or two dimensional convolution of a matrix variable
% in working memory.  It capitalizes on the sparsity structure of the
% problem and the separablity of multidimensional convolution with a Gaussian
% kernel by using one-dimensional convolutions and kernels that are
% restricted to non near-zero values.
%__________________________________________________________________________
% Copyright (C) 1999-2013 Wellcome Trust Centre for Neuroimaging

% Karl Friston
% $Id: spm_conv.m 5219 2013-01-29 17:07:07Z spm $


% assume isomorphic smoothing
%--------------------------------------------------------------------------
if nargin < 3; sy = sx; end