Objects.Area

import seaborn.objects as so
from seaborn import load_dataset
healthexp = (
    load_dataset("healthexp")
    .pivot(index="Year", columns="Country", values="Spending_USD")
    .interpolate()
    .stack()
    .rename("Spending_USD")
    .reset_index()
    .sort_values("Country")
)

p = so.Plot(healthexp, "Year", "Spending_USD").facet("Country", wrap=3)
p.add(so.Area())

p.add(so.Area(), color="Country")

p.add(so.Area(color=".5", edgewidth=2), edgecolor="Country")

p.add(so.Area(edgewidth=0)).add(so.Line())

p.add(so.Area(), x="Spending_USD", y="Year", orient="y")

(
    so.Plot(healthexp, "Year", "Spending_USD", color="Country")
    .add(so.Area(alpha=.7), so.Stack())
)