当绘图中使用3种以上的颜色时，在图例中会产生误导性的geom_smooth颜色

Please consider the following

请考虑以下事项

set.seed(28100)
random_data <- data.frame(x=rnorm(100),
                          y=rnorm(100),
                          colour=sample(c("a","b","c"),  100, replace=TRUE),
                          class=sample(c("alpha","beta"),  100, replace=TRUE))
require(ggplot2)
ggplot() +
  geom_smooth(data=random_data, aes(x=x, y=y, colour=colour, linetype=class), se=FALSE)
set.s