fix PrefetchingIter doc string error (#3909)
fix PrefetchingIter doc string error (#3909)


szha/mxnet,jermainewang/mxnet,jamesliu/mxnet,sergeykolychev/mxnet,nicklhy/mxnet,leezu/mxnet,crazy-cat/incubator-mxnet,indhub/mxnet,arank/mxnet,reminisce/mxnet,pluskid/mxnet,arank/mxnet,rishita/mxnet,hpi-xnor/BMXNet,madjam/mxnet,jiajiechen/mxnet,weleen/mxnet,yuruofeifei/mxnet,arikpoz/mxnet,EvanzzzZ/mxnet,madjam/mxnet,apaleyes/mxnet,ZihengJiang/mxnet,stefanhenneking/mxnet,ykim362/mxnet,piiswrong/mxnet,EvanzzzZ/mxnet,weleen/mxnet,kevinthesun/mxnet,larroy/mxnet,jennyzhang0215/incubator-mxnet,coder-james/mxnet,navrasio/mxnet,Prasad9/incubator-mxnet,piiswrong/mxnet,lxn2/mxnet,rahul003/mxnet,fullfanta/mxnet,jamesliu/mxnet,Mega-DatA-Lab/mxnet,rahul003/mxnet,sergeykolychev/mxnet,smolix/incubator-mxnet,nicklhy/mxnet,LinkHS/incubator-mxnet,rahul003/mxnet,Mega-DatA-Lab/mxnet,Guneet-Dhillon/mxnet,xcgoner/dist-mxnet,yuruofeifei/mxnet,ForkedReposBak/mxnet,fullfanta/mxnet,antoan2/incubator-mxnet,Mega-DatA-Lab/mxnet,szha/mxnet,wangyum/mxnet,solin319/incubator-mxnet,hesseltuinhof/mxnet,jiajiechen/mxnet,ZihengJiang/mxnet,ptrendx/mxnet,hpi-xnor/BMXNet,Guneet-Dhillon/mxnet,yajiedesign/mxnet,Guneet-Dhillon/mxnet,kevinthesun/mxnet,jiajiechen/mxnet,ptrendx/mxnet,piiswrong/mxnet,tornadomeet/mxnet,kevinthesun/mxnet,szha/mxnet,ykim362/mxnet,stefanhenneking/mxnet,eric-haibin-lin/mxnet,weleen/mxnet,LinkHS/incubator-mxnet,kkk669/mxnet,solin319/incubator-mxnet,tornadomeet/mxnet,wangyum/mxnet,LinkHS/incubator-mxnet,CodingCat/mxnet,mbaijal/incubator-mxnet,CodingCat/mxnet,kevinthesun/mxnet,tlby/mxnet,hotpxl/mxnet,ptrendx/mxnet,hotpxl/mxnet,leezu/mxnet,saurabh3949/mxnet,thirdwing/mxnet,DR08/mxnet,larroy/mxnet,Ldpe2G/mxnet,Prasad9/incubator-mxnet,precedenceguo/mxnet,jiajiechen/mxnet,TuSimple/mxnet,jiajiechen/mxnet,antoan2/incubator-mxnet,Ldpe2G/mxnet,madjam/mxnet,arank/mxnet,xcgoner/dist-mxnet,ZihengJiang/mxnet,zhreshold/mxnet,dmlc/mxnet,crazy-cat/incubator-mxnet,precedenceguo/mxnet,szha/mxnet,hesseltuinhof/mxnet,fullfanta/mxnet,TuSimple/mxnet,pluskid/mxnet,jennyzhang0215/incubator-mxnet,thirdwing/mxnet,coder-james/mxnet,yuruofeifei/mxnet,navrasio/mxnet,luoyetx/mxnet,coder-james/mxnet,tlby/mxnet,jermainewang/mxnet,wangyum/mxnet,lxn2/mxnet,ykim362/mxnet,zhreshold/mxnet,weleen/mxnet,dmlc/mxnet,ZihengJiang/mxnet,EvanzzzZ/mxnet,hotpxl/mxnet,wangyum/mxnet,yajiedesign/mxnet,indhub/mxnet,zhreshold/mxnet,solin319/incubator-mxnet,tornadomeet/mxnet,Prasad9/incubator-mxnet,kkk669/mxnet,rishita/mxnet,yajiedesign/mxnet,navrasio/mxnet,eric-haibin-lin/mxnet,leezu/mxnet,ShownX/incubator-mxnet,hotpxl/mxnet,rahul003/mxnet,ykim362/mxnet,leezu/mxnet,apaleyes/mxnet,navrasio/mxnet,indhub/mxnet,gautamkmr/incubator-mxnet,tlby/mxnet,stefanhenneking/mxnet,piiswrong/mxnet,stefanhenneking/mxnet,lxn2/mxnet,formath/mxnet,antoan2/incubator-mxnet,indhub/mxnet,likelyzhao/mxnet,precedenceguo/mxnet,hesseltuinhof/mxnet,ptrendx/mxnet,weleen/mxnet,thirdwing/mxnet,EvanzzzZ/mxnet,DickJC123/mxnet,likelyzhao/mxnet,mbaijal/incubator-mxnet,rishita/mxnet,EvanzzzZ/mxnet,arank/mxnet,rishita/mxnet,jamesliu/mxnet,mbaijal/incubator-mxnet,thirdwing/mxnet,dmlc/mxnet,wangyum/mxnet,rishita/mxnet,precedenceguo/mxnet,TuSimple/mxnet,saurabh3949/mxnet,larroy/mxnet,luoyetx/mxnet,xcgoner/dist-mxnet,ShownX/incubator-mxnet,ForkedReposBak/mxnet,ShownX/incubator-mxnet,ForkedReposBak/mxnet,sxjscience/mxnet,wangyum/mxnet,likelyzhao/mxnet,likelyzhao/mxnet,jamesliu/mxnet,piiswrong/mxnet,gautamkmr/incubator-mxnet,hotpxl/mxnet,eric-haibin-lin/mxnet,hpi-xnor/BMXNet,reminisce/mxnet,reminisce/mxnet,coder-james/mxnet,tlby/mxnet,rishita/mxnet,dmlc/mxnet,vikingMei/mxnet,formath/mxnet,nicklhy/mxnet,dmlc/mxnet,ForkedReposBak/mxnet,leezu/mxnet,sergeykolychev/mxnet,ykim362/mxnet,danithaca/mxnet,coder-james/mxnet,indhub/mxnet,formath/mxnet,fullfanta/mxnet,indhub/mxnet,thirdwing/mxnet,zhreshold/mxnet,sxjscience/mxnet,madjam/mxnet,Mega-DatA-Lab/mxnet,madjam/mxnet,Northrend/mxnet,thirdwing/mxnet,kevinthesun/mxnet,Mega-DatA-Lab/mxnet,piiswrong/mxnet,yajiedesign/mxnet,sxjscience/mxnet,gautamkmr/incubator-mxnet,mbaijal/incubator-mxnet,likelyzhao/mxnet,precedenceguo/mxnet,fullfanta/mxnet,weleen/mxnet,fullfanta/mxnet,LinkHS/incubator-mxnet,larroy/mxnet,eric-haibin-lin/mxnet,jermainewang/mxnet,ptrendx/mxnet,apaleyes/mxnet,CodingCat/mxnet,smolix/incubator-mxnet,formath/mxnet,DR08/mxnet,nicklhy/mxnet,crazy-cat/incubator-mxnet,jennyzhang0215/incubator-mxnet,yajiedesign/mxnet,ForkedReposBak/mxnet,larroy/mxnet,DR08/mxnet,CodingCat/mxnet,xcgoner/dist-mxnet,DR08/mxnet,EvanzzzZ/mxnet,navrasio/mxnet,rishita/mxnet,likelyzhao/mxnet,mbaijal/incubator-mxnet,eric-haibin-lin/mxnet,luoyetx/mxnet,Northrend/mxnet,sxjscience/mxnet,navrasio/mxnet,jamesliu/mxnet,pluskid/mxnet,yuruofeifei/mxnet,larroy/mxnet,indhub/mxnet,solin319/incubator-mxnet,antoan2/incubator-mxnet,solin319/incubator-mxnet,CodingCat/mxnet,fullfanta/mxnet,stefanhenneking/mxnet,yuruofeifei/mxnet,EvanzzzZ/mxnet,hpi-xnor/BMXNet,fullfanta/mxnet,pluskid/mxnet,rishita/mxnet,crazy-cat/incubator-mxnet,weleen/mxnet,tornadomeet/mxnet,zhreshold/mxnet,tornadomeet/mxnet,TuSimple/mxnet,Northrend/mxnet,lxn2/mxnet,ShownX/incubator-mxnet,mbaijal/incubator-mxnet,sergeykolychev/mxnet,ShownX/incubator-mxnet,reminisce/mxnet,lxn2/mxnet,DickJC123/mxnet,pluskid/mxnet,rishita/mxnet,yuruofeifei/mxnet,Northrend/mxnet,madjam/mxnet,nicklhy/mxnet,tornadomeet/mxnet,ForkedReposBak/mxnet,pluskid/mxnet,Ldpe2G/mxnet,stefanhenneking/mxnet,madjam/mxnet,wangyum/mxnet,Ldpe2G/mxnet,indhub/mxnet,crazy-cat/incubator-mxnet,apaleyes/mxnet,sxjscience/mxnet,ShownX/incubator-mxnet,arikpoz/mxnet,jennyzhang0215/incubator-mxnet,ptrendx/mxnet,EvanzzzZ/mxnet,jennyzhang0215/incubator-mxnet,Ldpe2G/mxnet,kkk669/mxnet,TuSimple/mxnet,dmlc/mxnet,navrasio/mxnet,larroy/mxnet,hotpxl/mxnet,jamesliu/mxnet,tlby/mxnet,jennyzhang0215/incubator-mxnet,CodingCat/mxnet,coder-james/mxnet,xcgoner/dist-mxnet,arank/mxnet,LinkHS/incubator-mxnet,sergeykolychev/mxnet,tlby/mxnet,jiajiechen/mxnet,arikpoz/mxnet,Guneet-Dhillon/mxnet,reminisce/mxnet,TuSimple/mxnet,hotpxl/mxnet,nicklhy/mxnet,Guneet-Dhillon/mxnet,danithaca/mxnet,Prasad9/incubator-mxnet,jermainewang/mxnet,ShownX/incubator-mxnet,jamesliu/mxnet,tlby/mxnet,Prasad9/incubator-mxnet,apaleyes/mxnet,luoyetx/mxnet,ZihengJiang/mxnet,lxn2/mxnet,precedenceguo/mxnet,CodingCat/mxnet,jermainewang/mxnet,ykim362/mxnet,jiajiechen/mxnet,jermainewang/mxnet,zhreshold/mxnet,smolix/incubator-mxnet,reminisce/mxnet,Mega-DatA-Lab/mxnet,DR08/mxnet,jennyzhang0215/incubator-mxnet,larroy/mxnet,szha/mxnet,stefanhenneking/mxnet,ykim362/mxnet,saurabh3949/mxnet,dmlc/mxnet,mbaijal/incubator-mxnet,Northrend/mxnet,rahul003/mxnet,arikpoz/mxnet,Prasad9/incubator-mxnet,piiswrong/mxnet,apaleyes/mxnet,LinkHS/incubator-mxnet,jermainewang/mxnet,xcgoner/dist-mxnet,ZihengJiang/mxnet,kkk669/mxnet,Northrend/mxnet,coder-james/mxnet,hotpxl/mxnet,reminisce/mxnet,hesseltuinhof/mxnet,apache/incubator-mxnet,sxjscience/mxnet,hpi-xnor/BMXNet,leezu/mxnet,jamesliu/mxnet,solin319/incubator-mxnet,vikingMei/mxnet,apaleyes/mxnet,Prasad9/incubator-mxnet,eric-haibin-lin/mxnet,reminisce/mxnet,gautamkmr/incubator-mxnet,likelyzhao/mxnet,yajiedesign/mxnet,kkk669/mxnet,crazy-cat/incubator-mxnet,sergeykolychev/mxnet,CodingCat/mxnet,TuSimple/mxnet,Mega-DatA-Lab/mxnet,apache/incubator-mxnet,pluskid/mxnet,ptrendx/mxnet,DR08/mxnet,gautamkmr/incubator-mxnet,dmlc/mxnet,vikingMei/mxnet,precedenceguo/mxnet,Guneet-Dhillon/mxnet,antoan2/incubator-mxnet,antoan2/incubator-mxnet,yajiedesign/mxnet,jiajiechen/mxnet,kevinthesun/mxnet,rahul003/mxnet,luoyetx/mxnet,leezu/mxnet,hesseltuinhof/mxnet,precedenceguo/mxnet,madjam/mxnet,mbaijal/incubator-mxnet,crazy-cat/incubator-mxnet,eric-haibin-lin/mxnet,ForkedReposBak/mxnet,xcgoner/dist-mxnet,tlby/mxnet,DR08/mxnet,tornadomeet/mxnet,DR08/mxnet,tornadomeet/mxnet,antoan2/incubator-mxnet,wangyum/mxnet,smolix/incubator-mxnet,mbaijal/incubator-mxnet,gautamkmr/incubator-mxnet,zhreshold/mxnet,szha/mxnet,Mega-DatA-Lab/mxnet,vikingMei/mxnet,rahul003/mxnet,jiajiechen/mxnet,sxjscience/mxnet,Guneet-Dhillon/mxnet,yajiedesign/mxnet,Prasad9/incubator-mxnet,LinkHS/incubator-mxnet,hesseltuinhof/mxnet,piiswrong/mxnet,jennyzhang0215/incubator-mxnet,szha/mxnet,gautamkmr/incubator-mxnet,hpi-xnor/BMXNet,TuSimple/mxnet,crazy-cat/incubator-mxnet,nicklhy/mxnet,danithaca/mxnet,arikpoz/mxnet,kevinthesun/mxnet,szha/mxnet,saurabh3949/mxnet,Mega-DatA-Lab/mxnet,ShownX/incubator-mxnet,Northrend/mxnet,apache/incubator-mxnet,Prasad9/incubator-mxnet,crazy-cat/incubator-mxnet,xcgoner/dist-mxnet,wangyum/mxnet,lxn2/mxnet,danithaca/mxnet,rahul003/mxnet,smolix/incubator-mxnet,weleen/mxnet,kevinthesun/mxnet,Northrend/mxnet,formath/mxnet,formath/mxnet,nicklhy/mxnet,rahul003/mxnet,formath/mxnet,danithaca/mxnet,sxjscience/mxnet,eric-haibin-lin/mxnet,kkk669/mxnet,lxn2/mxnet,ZihengJiang/mxnet,yuruofeifei/mxnet,vikingMei/mxnet,ykim362/mxnet,sergeykolychev/mxnet,weleen/mxnet,formath/mxnet,ptrendx/mxnet,coder-james/mxnet,arank/mxnet,Ldpe2G/mxnet,Ldpe2G/mxnet,solin319/incubator-mxnet,arank/mxnet,pluskid/mxnet,jermainewang/mxnet,TuSimple/mxnet,TuSimple/mxnet,antoan2/incubator-mxnet,navrasio/mxnet,vikingMei/mxnet,gautamkmr/incubator-mxnet,lxn2/mxnet,kkk669/mxnet,precedenceguo/mxnet,Ldpe2G/mxnet,yajiedesign/mxnet,ptrendx/mxnet,jermainewang/mxnet,luoyetx/mxnet,larroy/mxnet,hpi-xnor/BMXNet,danithaca/mxnet,ForkedReposBak/mxnet,ZihengJiang/mxnet,solin319/incubator-mxnet,apaleyes/mxnet,Ldpe2G/mxnet,dmlc/mxnet,saurabh3949/mxnet,apaleyes/mxnet,yuruofeifei/mxnet,DR08/mxnet,leezu/mxnet,likelyzhao/mxnet,DickJC123/mxnet,hesseltuinhof/mxnet,sxjscience/mxnet,madjam/mxnet,gautamkmr/incubator-mxnet,thirdwing/mxnet,luoyetx/mxnet,LinkHS/incubator-mxnet,kkk669/mxnet,szha/mxnet,pluskid/mxnet,kkk669/mxnet,smolix/incubator-mxnet,jennyzhang0215/incubator-mxnet,ShownX/incubator-mxnet,navrasio/mxnet,stefanhenneking/mxnet,solin319/incubator-mxnet,leezu/mxnet,danithaca/mxnet,hpi-xnor/BMXNet,indhub/mxnet,thirdwing/mxnet,vikingMei/mxnet,arikpoz/mxnet,ykim362/mxnet,zhreshold/mxnet,vikingMei/mxnet,luoyetx/mxnet,saurabh3949/mxnet,Guneet-Dhillon/mxnet,stefanhenneking/mxnet,EvanzzzZ/mxnet,piiswrong/mxnet,hotpxl/mxnet,eric-haibin-lin/mxnet,hpi-xnor/BMXNet,apache/incubator-mxnet,smolix/incubator-mxnet,antoan2/incubator-mxnet,arikpoz/mxnet,Northrend/mxnet,saurabh3949/mxnet,yuruofeifei/mxnet,hesseltuinhof/mxnet,danithaca/mxnet,ForkedReposBak/mxnet,reminisce/mxnet,DickJC123/mxnet,sergeykolychev/mxnet,reminisce/mxnet,LinkHS/incubator-mxnet,hesseltuinhof/mxnet,zhreshold/mxnet,formath/mxnet,tornadomeet/mxnet,CodingCat/mxnet,smolix/incubator-mxnet,smolix/incubator-mxnet,saurabh3949/mxnet,arikpoz/mxnet,ptrendx/mxnet,vikingMei/mxnet,xcgoner/dist-mxnet,danithaca/mxnet,jamesliu/mxnet,arank/mxnet,thirdwing/mxnet,sergeykolychev/mxnet,tlby/mxnet,arank/mxnet,saurabh3949/mxnet,nicklhy/mxnet,luoyetx/mxnet,ZihengJiang/mxnet,coder-james/mxnet,fullfanta/mxnet,arikpoz/mxnet,kevinthesun/mxnet,tlby/mxnet,Guneet-Dhillon/mxnet,likelyzhao/mxnet