fixed caching bug with args having Nones
fixed caching bug with args having Nones

avehtari/GPy,buntyke/GPy,gusmaogabriels/GPy,befelix/GPy,SheffieldML/GPy,maaskola/GPy,mikecroucher/GPy,TianpeiLuke/GPy,ysekky/GPy,mikecroucher/GPy,avehtari/GPy,jameshensman/GPy,dhhjx880713/GPy,esiivola/GPYgradients,buntyke/GPy,maaskola/GPy,fivejjs/GPy,mikecroucher/GPy,AlexGrig/GPy,SheffieldML/GPy,Dapid/GPy,befelix/GPy,beckdaniel/GPy,jameshensman/GPy,ysekky/GPy,buntyke/GPy,ptonner/GPy,Dapid/GPy,ptonner/GPy,strongh/GPy,AlexGrig/GPy,befelix/GPy,TianpeiLuke/GPy,dhhjx880713/GPy,SheffieldML/GPy,beckdaniel/GPy,Dapid/GPy,ysekky/GPy,SheffieldML/GPy,gusmaogabriels/GPy,jameshensman/GPy,fivejjs/GPy,maaskola/GPy,ptonner/GPy,jameshensman/GPy,TianpeiLuke/GPy,Dapid/GPy,befelix/GPy,buntyke/GPy,PredictiveScienceLab/GPy,ptonner/GPy,esiivola/GPYgradients,AlexGrig/GPy,ysekky/GPy,PredictiveScienceLab/GPy,avehtari/GPy,PredictiveScienceLab/GPy,beckdaniel/GPy,dhhjx880713/GPy,gusmaogabriels/GPy,maaskola/GPy,fivejjs/GPy,strongh/GPy,AlexGrig/GPy,strongh/GPy,dhhjx880713/GPy,PredictiveScienceLab/GPy,avehtari/GPy,beckdaniel/GPy,esiivola/GPYgradients,mikecroucher/GPy,esiivola/GPYgradients