$(2)$ The build$\_$lambda uses self.m$,$ self.b and returns self.fn $($ x : xm $+$ b$)$ so that we can use the line as a function. You are free to use this in $\_\_$init$()\_\_$ if you deem it useful. $(3)$ The $\_\_$and$()\_\_$ allows us to override &$.$ This is used to determine if we have two lines: if they intersect, then a tuple returned with the coordiates of the point of intersection; if lines are parallel then the tuple $("$parallel$",)$ is returned; if lines are the same then tuple $("$same$",)$ is returned. $(4)$ The $\_\_$call$()\_\_$ function allows us to use the objects as a function call. For example,