If you are creating a new geom, stat, position, or scale in another package,
you'll need to extend from ggplot2::Geom, ggplot2::Stat,
ggplot2::Position, or ggplot2::Scale.
AAListAn object of class AAList (inherits from ggproto, gg) of length 6.
top, left, right, bottom, etc.
When TRUE, only get annotations whose side are set to that side. When FALSE (default), also get those that are waiver.