Patchworklib inadvertently removes subtitles in ggplot objects drawn by plotnine

[oracle5th]

Code to reproduce:

import patchworklib as pw
from plotnine import (ggplot, aes, geom_point, geom_boxplot, labs)
from plotnine.data import mtcars

g1 = pw.load_ggplot(ggplot(mtcars) 
                    + geom_point(aes("mpg", "disp"))
                    + labs(title='title1', subtitle='subtitle1'),
                    figsize=(2,3))
g2 = pw.load_ggplot(ggplot(mtcars) 
                    + geom_boxplot(aes("gear", "disp", group="gear"))
                    + labs(title='title2', subtitle='subtitle2'),
                    figsize=(2,3))

g = (g1|g2)
g.savefig('test.pdf')