Minor fix for deepcopy
Minor fix for deepcopy

dmadeka/bqplot,ChakriCherukuri/bqplot,ssunkara1/bqplot,bloomberg/bqplot,ChakriCherukuri/bqplot,rmenegaux/bqplot,dmadeka/bqplot,ssunkara1/bqplot,bloomberg/bqplot,rmenegaux/bqplot,SylvainCorlay/bqplot,SylvainCorlay/bqplot,SylvainCorlay/bqplot,bloomberg/bqplot,ChakriCherukuri/bqplot