Add ToC dropdown sync'd to H1...3 header notebook cells
Add ToC dropdown sync'd to H1...3 header notebook cells

craigcitro/datalab,craigcitro/datalab,parthea/datalab,parthea/datalab,parthea/datalab,yebrahim/datalab,yebrahim/datalab,googledatalab/datalab,yebrahim/datalab,googledatalab/datalab,googledatalab/datalab,craigcitro/datalab,googledatalab/datalab,craigcitro/datalab,parthea/datalab,parthea/datalab,parthea/datalab,yebrahim/datalab,googledatalab/datalab,yebrahim/datalab,craigcitro/datalab,googledatalab/datalab