flagging/masking

current implementation

decorator	handles	masking	sqeeze history
flagging()	data	"field"/"all"/None	yes (but not needed)
flagging()	flags	"field"/"all"/None	yes
processing()	index		no (not possible)

suggested implementation

decorator	handles	datamask	sqeeze history
register()	"data"	"field"/"all"/None	no (not needed)
register()	"flags"	"field"/"all"/None	yes
register()	"index"	"field"/"all"/None	no (not possible)