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: step0_define_paths.m
    path of file: ./repos/md-dmri/examples/pipeline
    
    the code of the file until where you have to start completion: function ps = step0_define_paths()
% function ps = step0_define_paths()
%
% Before you begin, download the data from here 
% https://github.com/filip-szczepankiewicz/Szczepankiewicz_DIB_2019

    
function ps = step0_define_paths()
% function ps = step0_define_paths()
%
% Before you begin, download the data from here 
% https://github.com/filip-szczepankiewicz/Szczepankiewicz_DIB_2019
%
% Then set the paths below accordingly
%
% Output: A paths structure


% Connect to the data (bp - base path, ip - input path, op - output path)
ps.bp = 'Szczepankiewicz_DIB_2019'; % <- download from Github, see above
ps.ip = fullfile(ps.bp, 'DATA', 'brain', 'NII'); % <- actual input data
ps.op = fullfile(ps.bp, 'processed', 'brain'); % <- store output here
ps.zp = fullfile(ps.bp, 'tmp'); % <- store temporary files here

if ((~exist(ps.bp, 'dir')) || ...
        (~exist(ps.ip, 'dir')))
    error('Data not found at specified folder. See instructions in header.')
end