add nullValue and ColOp to ContextBase for Map
add nullValue and ColOp to ContextBase for Map

arq5x/bedtools2,arq5x/bedtools2,jmarshall/bedtools2,jmarshall/bedtools2,jmarshall/bedtools2,jmarshall/bedtools2,arq5x/bedtools2,arq5x/bedtools2,jmarshall/bedtools2,arq5x/bedtools2