I was using the Enable transform.
My build failed due to the following line.
#include "transforms/transform.h"

When I changed it to
#include "transform.h"
then the build was fine and function was also fine.

I suspect there was a previous refactoring and this was missed.
I cannot find any other examples of this transform being used so maybe I am the first to use it.

My Environment: PlatformIO

I would fix and submit but I am new to sensesp and git so I will defer to someone else.

Thanks in advance