Remove use of abc.ABCMeta due to cloudpickle issue.
Remove use of abc.ABCMeta due to cloudpickle issue.

cloudpickle runs into issues while pickling subclasses of AccumulatorParam,
which may be related to this Python issue:

    http://bugs.python.org/issue7689

This seems hard to fix and the ABCMeta wasn't necessary, so I removed it.

pronix/spark,lyogavin/spark,yanboliang/spark,maropu/spark,zero323/spark,pgandhi999/spark,techaddict/spark,cin/spark,ptkool/spark,bdrillard/spark,rikima/spark,ron8hu/spark,BryanCutler/spark,ron8hu/spark,sahilTakiar/spark,goldmedal/spark,nilsgrabbert/spark,alunarbeach/spark,dbtsai/spark,minixalpha/spark,wgpshashank/spark,sachintyagi22/spark,aray/spark,andrewor14/iolap,kimoonkim/spark,huang1900/spark,darionyaphet/spark,andrewor14/spark,kimoonkim/spark,BryanCutler/spark,ioana-delaney/spark,saltstar/spark,andrewor14/iolap,aray/spark,big-pegasus/spark,liutang123/spark,Aegeaner/spark,vinodkc/spark,maropu/spark,maropu/spark,esi-mineset/spark,ConeyLiu/spark,nlalevee/spark,mzl9039/spark,minixalpha/spark,zzcclp/spark,rekhajoshm/spark,shubhamchopra/spark,kimoonkim/spark,michalsenkyr/spark,milliman/spark,wgpshashank/spark,brad-kaiser/spark,wangmiao1981/spark,jiangxb1987/spark,shaneknapp/spark,pgandhi999/spark,actuaryzhang/spark,rikima/spark,jianran/spark,patrick-nicholson/spark,metamx/spark,UndeadBaneGitHub/spark,joseph-torres/spark,rednaxelafx/apache-spark,rjpower/spark,skonto/spark,nchammas/spark,loneknightpy/spark,szhem/spark,UndeadBaneGitHub/spark,aokolnychyi/spark,nilsgrabbert/spark,hhbyyh/spark,Panos-Bletsos/spark-cost-model-optimizer,debugger87/spark,JoshRosen/spark,huang1900/spark,holdenk/spark,wzhfy/spark,joseph-torres/spark,rekhajoshm/spark,techaddict/spark,kissmetrics/spark,adrian-ionescu/apache-spark,vax11780/spark,rezasafi/spark,spark-test/spark,panfengfeng/spark,ibm-research-ireland/sparkoscope,szhem/spark,LantaoJin/spark,someorz/spark,darionyaphet/spark,1haodian/spark,chuckchen/spark,WindCanDie/spark,janewangfb/spark,mahak/spark,big-pegasus/spark,andrewor14/iolap,ConeyLiu/spark,SHASHANKB/spark,tejasapatil/spark,mdespriee/spark,bdrillard/spark,ericvandenbergfb/spark,ahnqirage/spark,xuanyuanking/spark,rezasafi/spark,aray/spark,nchammas/spark,vax11780/spark,ptkool/spark,shubhamchopra/spark,xuanyuanking/spark,mdespriee/spark,ibm-research-ireland/sparkoscope,jianran/spark,witgo/spark,nchammas/spark,setjet/spark,tengpeng/spark,michalsenkyr/spark,tejasapatil/spark,liutang123/spark,nlalevee/spark,cin/spark,vinodkc/spark,markhamstra/spark,brad-kaiser/spark,ioana-delaney/spark,mike0sv/spark,ericvandenbergfb/spark,zzcclp/spark,jrshust/spark,rekhajoshm/spark,eyalfa/spark,map222/spark,akopich/spark,ddna1021/spark,kiszk/spark,ConeyLiu/spark,map222/spark,zhouyejoe/spark,BryanCutler/spark,ron8hu/spark,kevinyu98/spark,milliman/spark,SHASHANKB/spark,rednaxelafx/apache-spark,chuckchen/spark,witgo/spark,rikima/spark,wzhfy/spark,gioenn/xSpark,pronix/spark,techaddict/spark,nchammas/spark,metamx/spark,ron8hu/spark,icexelloss/spark,saturday-shi/spark,sachintyagi22/spark,MLnick/spark,liutang123/spark,rednaxelafx/apache-spark,ptkool/spark,skonto/spark,actuaryzhang/spark,highfei2011/spark,metamx/spark,wangyum/spark,aosagie/spark,zuotingbing/spark,sureshthalamati/spark,lxsmnv/spark,publicRoman/spark,lxsmnv/spark,BryanCutler/spark,liutang123/spark,JerryLead/spark,wzhfy/spark,akopich/spark,mahak/spark,zero323/spark,ueshin/apache-spark,saturday-shi/spark,rednaxelafx/apache-spark,sureshthalamati/spark,kiszk/spark,sureshthalamati/spark,ConeyLiu/spark,SHASHANKB/spark,big-pegasus/spark,dhruve/spark,WeichenXu123/spark,mike0sv/spark,icexelloss/spark,zuotingbing/spark,gioenn/xSpark,rekhajoshm/spark,hvanhovell/spark,ueshin/apache-spark,guoxiaolongzte/spark,kiszk/spark,janewangfb/spark,yanboliang/spark,srowen/spark,caneGuy/spark,someorz/spark,saturday-shi/spark,guoxiaolongzte/spark,kiszk/spark,debugger87/spark,jrshust/spark,aosagie/spark,byakuinss/spark,jkbradley/spark,zzcclp/spark,SHASHANKB/spark,cloud-fan/spark,shaneknapp/spark,chuckchen/spark,taroplus/spark,techaddict/spark,srowen/spark,hhbyyh/spark,apache/spark,ron8hu/spark,actuaryzhang/spark,witgo/spark,ueshin/apache-spark,big-pegasus/spark,guoxiaolongzte/spark,goldmedal/spark,witgo/spark,Aegeaner/spark,koeninger/spark,hvanhovell/spark,SnappyDataInc/spark,SnappyDataInc/spark,markhamstra/spark,shaneknapp/spark,ajaysaini725/spark,tengpeng/spark,jrshust/spark,JerryLead/spark,WindCanDie/spark,ajaysaini725/spark,ahnqirage/spark,andrewor14/spark,WeichenXu123/spark,shuangshuangwang/spark,stanzhai/spark,metamx/spark,holdenk/spark,apache-spark-on-k8s/spark,JerryLead/spark,andrewor14/iolap,loneknightpy/spark,ajaysaini725/spark,patrick-nicholson/spark,xuanyuanking/spark,WindCanDie/spark,stanzhai/spark,MLnick/spark,lxsmnv/spark,nilsgrabbert/spark,ueshin/apache-spark,nchammas/spark,saturday-shi/spark,lyogavin/spark,aray/spark,bdrillard/spark,bOOm-X/spark,eyalfa/spark,nchammas/spark,ddna1021/spark,narahari92/spark,andrewor14/spark,BryanCutler/spark,shaneknapp/spark,andrewor14/iolap,sryza/spark,akopich/spark,cloud-fan/spark,apache/spark,WindCanDie/spark,panfengfeng/spark,zero323/spark,highfei2011/spark,rikima/spark,taroplus/spark,spark-test/spark,skonto/spark,brad-kaiser/spark,szhem/spark,janewangfb/spark,WeichenXu123/spark,aokolnychyi/spark,zzcclp/spark,WeichenXu123/spark,sahilTakiar/spark,zuotingbing/s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ark,rednaxelafx/apache-spark,1haodian/spark,narahari92/spark,SnappyDataInc/spark,kissmetrics/spark,holdenk/spark,bOOm-X/spark,Panos-Bletsos/spark-cost-model-optimizer,someorz/spark,apache/spark,JoshRosen/spark,chuckchen/spark,gengliangwang/spark,wangmiao1981/spark,UndeadBaneGitHub/spark,jlopezmalla/spark,spark-test/spark,stanzhai/spark,eyalfa/spark,mike0sv/spark,SnappyDataInc/spark,gioenn/xSpark,brad-kaiser/spark,panfengfeng/spark,shuangshuangwang/spark,jlopezmalla/spark,vax11780/spark,tengpeng/spark,kiszk/spark,shuangshuangwang/spark,LantaoJin/spark,map222/spark,bdrillard/spark,gengliangwang/spark,loneknightpy/spark,narahari92/spark,WindCanDie/spark,sureshthalamati/spark,HyukjinKwon/spark,wangmiao1981/spark,esi-mineset/spark,JoshRosen/spark,cloud-fan/spark,JerryLead/spark,jlopezmalla/spark,sahilTakiar/spark,nlalevee/spark,ahnqirage/spark,dotunolafunmiloye/spark,sahilTakiar/spark,byakuinss/spark,SHASHANKB/spark,ericvandenbergfb/spark,wangmiao1981/spark,vinodkc/spark,SHASHANKB/spark,rezasafi/spark,ron8hu/spark,alunarbeach/spark,publicRoman/spark,ConeyLiu/spark,lxsmnv/spark,BryanCutler/spark,taroplus/spark,huang1900/spark,markhamstra/spark,facaiy/spark,milliman/spark,bOOm-X/spark,kevinyu98/spark,aokolnychyi/spark,JoshRosen/spark,gengliangwang/spark,patrick-nicholson/spark,szhem/spark,wzhfy/spark,lvdongr/spark,sachintyagi22/spark,kevinyu98/spark,andrewor14/spark,aokolnychyi/spark,someorz/spark,sryza/spark,saturday-shi/spark,LantaoJin/spark,huang1900/spark,nlalevee/spark,jiangxb1987/spark,maropu/spark,SnappyDataInc/spark,dotunolafunmiloye/spark,dbtsai/spark,skonto/spark,huang1900/spark,kimoonkim/spark,adrian-ionescu/apache-spark,milliman/spark,saltstar/spark,tengpeng/spark,narahari92/spark,dbtsai/spark,apache-spark-on-k8s/spark,aosagie/spark,haowu80s/spark,koeninger/spark,chuckchen/spark,map222/spark,publicRoman/spark,jlopezmalla/spark,janewangfb/spark,hhbyyh/spark,MLnick/spark,jkbradley/spark,panfengfeng/spark,aosagie/spark,haowu80s/spark,sahilTakiar/spark,lxsmnv/spark,ajaysaini725/spark,loneknightpy/spark,facaiy/spark,techaddict/spark,tejasapatil/spark,yanboliang/spark,jiangxb1987/spark,narahari92/spark,tengpeng/spark,zero323/spark,rikima/spark,sachintyagi22/spark,liyichao/spark,caneGuy/spark,dongjoon-hyun/spark,eyalfa/spark,cin/spark,liutang123/spark,apache-spark-on-k8s/spark,loneknightpy/spark,publicRoman/spark,rezasafi/spark,janewangfb/spark,rikima/spark,joseph-torres/spark,apache/spark,byakuinss/spark,bravo-zhang/spark,poffuomo/spark,guoxiaolongzte/spark,zuotingbing/spark,big-pegasus/spark,guoxiaolongzte/spark,dhruve/spark,liyichao/spark,esi-mineset/spark,tejasapatil/spark,sahilTakiar/spark,LantaoJin/spark,alunarbeach/spark,ericvandenbergfb/spark,facaiy/spark,kimoonkim/spark,mahak/spark,ahnqirage/spark,hvanhovell/spark,jlopezmalla/spark,Panos-Bletsos/spark-cost-model-optimizer,skonto/spark,saltstar/spark,pronix/spark,mahak/spark,debugger87/spark,mike0sv/spark,mkolod/incubator-spark,loneknightpy/spark,pgandhi999/spark,byakuinss/spark,bravo-zhang/spark,wzhfy/spark,dhruve/spark,shubhamchopra/spark,BryanCutler/spark,publicRoman/spark,minixalpha/spark,liyichao/spark,gioenn/xSpark,wangyum/spark,apache-spark-on-k8s/spark,actuaryzhang/spark,srowen/spark,guoxiaolongzte/spark,facaiy/spark,pronix/spark,LantaoJin/spark,JerryLead/spark,aosagie/spark,icexelloss/spark,cloud-fan/spark,mike0sv/spark,maropu/spark,Aegeaner/spark,vax11780/spark,stanzhai/spark,setjet/spark,kissmetrics/spark,spark-test/spark,janewangfb/spark,gengliangwang/spark,MLnick/spark,haowu80s/spark,jlopezmalla/spark,shuangshuangwang/spark,rjpower/spark,mkolod/incubator-spark,setjet/spark,markhamstra/spark,holdenk/spark,techaddict/spark,WindCanDie/spark,esi-mineset/spark,facaiy/spark,taroplus/spark,cin/spark,saturday-shi/spark,ericvandenbergfb/spark,jianran/spark,dbtsai/spark,vax11780/spark,kevinyu98/spark,lyogavin/spark,sureshthalamati/spark,liutang123/spark,chuckchen/spark,aosagie/spark,shuangshuangwang/spark,actuaryzhang/spark,JoshRosen/spark,holdenk/spark,apache/spark,JerryLead/spark,actuaryzhang/spark,stanzhai/spark,kevinyu98/spark,taroplus/spark,wangmiao1981/spark,esi-mineset/spark,michalsenkyr/spark,highfei2011/spark,zhouyejoe/spark,SnappyDataInc/spark,joseph-torres/spark,pgandhi999/spark,shaneknapp/spark,wangyum/spark,goldmedal/spark,wangyum/spark,akopich/spark,ron8hu/spark,andrewor14/spark,vinodkc/spark,yanboliang/spark,michalsenkyr/spark,jkbradley/spark,dongjoon-hyun/spark,poffuomo/spark,adrian-ionescu/apache-spark,sryza/spark,bdrillard/spark,caneGuy/spark,dbtsai/spark,zero323/spark,saltstar/spark,hhbyyh/spark,markhamstra/spark,SnappyDataInc/spark,caneGuy/spark,hvanhovell/spark,gengliangwang/spark,mzl9039/spark,xuanyuanking/spark,rjpower/spark,minixalpha/spark,ibm-research-ireland/sparkoscope,cloudera/spark,mdespriee/spark,panfengfeng/spark,wzhfy/spark,setjet/spark,kevinyu98/spark,srowen/spark,ptkool/spark,rezasafi/spark,brad-kaiser/spark,stanzhai/spark,ahnqirage/spark,wgpshashank/spark,liyichao/spark,wgpshashank/spark,ConeyLiu/spark,cloudera/s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