from sectionproperties.pre.library import rectangular_section
from sectionproperties.pre.library import channel_section

geom1 = channel_section(d=200, b=75, t_f=12, t_w=6, r=12, n_r=8)
geom2 = rectangular_section(d=20, b=133)
compound = geom1 + geom2.align_center(align_to=geom1).align_to(
    other=geom1, on="top"
)
compound.mirror_section(axis="y", mirror_point=(0,0)).plot_geometry()