Fix code quality issue in util/data_structures.coffee
Fix code quality issue in util/data_structures.coffee

azjps/bokeh,DuCorey/bokeh,draperjames/bokeh,mindriot101/bokeh,aiguofer/bokeh,DuCorey/bokeh,bokeh/bokeh,draperjames/bokeh,mindriot101/bokeh,schoolie/bokeh,phobson/bokeh,rs2/bokeh,Karel-van-de-Plassche/bokeh,ptitjano/bokeh,philippjfr/bokeh,schoolie/bokeh,dennisobrien/bokeh,philippjfr/bokeh,rs2/bokeh,aavanian/bokeh,Karel-van-de-Plassche/bokeh,ericmjl/bokeh,jakirkham/bokeh,ericmjl/bokeh,philippjfr/bokeh,timsnyder/bokeh,rs2/bokeh,dennisobrien/bokeh,DuCorey/bokeh,azjps/bokeh,percyfal/bokeh,schoolie/bokeh,aiguofer/bokeh,phobson/bokeh,philippjfr/bokeh,ptitjano/bokeh,jakirkham/bokeh,aavanian/bokeh,jakirkham/bokeh,schoolie/bokeh,jakirkham/bokeh,stonebig/bokeh,timsnyder/bokeh,phobson/bokeh,timsnyder/bokeh,jakirkham/bokeh,aiguofer/bokeh,percyfal/bokeh,dennisobrien/bokeh,bokeh/bokeh,aiguofer/bokeh,bokeh/bokeh,ptitjano/bokeh,stonebig/bokeh,percyfal/bokeh,ericmjl/bokeh,azjps/bokeh,mindriot101/bokeh,azjps/bokeh,timsnyder/bokeh,aavanian/bokeh,timsnyder/bokeh,aavanian/bokeh,phobson/bokeh,stonebig/bokeh,DuCorey/bokeh,dennisobrien/bokeh,ericmjl/bokeh,bokeh/bokeh,phobson/bokeh,draperjames/bokeh,aavanian/bokeh,rs2/bokeh,mindriot101/bokeh,percyfal/bokeh,Karel-van-de-Plassche/bokeh,Karel-van-de-Plassche/bokeh,ptitjano/bokeh,dennisobrien/bokeh,ptitjano/bokeh,percyfal/bokeh,azjps/bokeh,philippjfr/bokeh,schoolie/bokeh,aiguofer/bokeh,draperjames/bokeh,Karel-van-de-Plassche/bokeh,bokeh/bokeh,draperjames/bokeh,rs2/bokeh,DuCorey/bokeh,ericmjl/bokeh,stonebig/bokeh