x::AbstractVector
ylow::AbstractVector
ylow::AbstractVector
group::AbstractVector

x = [0,1,2,3,4,5,6,7,8,9,0,1,2,3,4,5,6,7,8,9]
y = [28, 43, 81, 19, 52, 24, 87, 17, 68, 49, 55, 91, 53, 87, 48, 49, 66, 27, 16, 15]
g = [0,0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,1,1,1,1]
a = ribbonplot(x = x, ylow = 0.9y, yhigh=1.1y, group = g)