def cal$\_$area$($base$,$ height, mode$=$"rectangle"$)$: # Check if the base or height is negative if base $<0$ or height $<0$: return "Base and height must be non$-$negative values." # Check the mode and calculate the area accordingly if mode $==$ "rectangle": area $=$ base $*$ height return f$"$The area of the rectangle is: $\{$area$\}"$ elif mode $==$ "triangle": area $=0\mathrm{.}5*$ base $*$ height return f$"$The area of the triangle is: $\{$area$\}"$ else: return "Invalid mode. Please use 'rectangle' or 'triangle'."