"group" "data"
"a" 0
"a" 0
"a" 0
"a" 0
"a" 0
"a" 0
"a" 0
"a" 0
"a" 0
"a" 0
"a" 0
"a" 0
"a" 0
"a" 0
"a" 0
"a" 0
"a" 0
"a" 1
"a" 1
"a" 2
"b" 1
"b" 1
"b" 1
"b" 3