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: formulate_data.m
    path of file: ./repos/deeplearningsourceseparation/codes/timit
    
    the code of the file until where you have to start completion: function  varargout = formulate_data(train1, train2, eI, mode)
% Copyright (c) 2014-present University of Illinois at Urbana-Champaign

    
function  varargout = formulate_data(train1, train2, eI, mode)
% Copyright (c) 2014-present University of Illinois at Urbana-Champaign
% All rights reserved.
% 		
% Developed by:     Po-Sen Huang, Paris Smaragdis
%                   Department of Electrical and Computer Engineering
%                   Department of Computer Science
%
% eI.winSize: Size of window
% eI.seqLen: unique lengths (in ascend