How to get field of view of HMD (Vive) reliably? GetFieldOfView(x,y) returns 0,0

I’m trying to get the field of view, but it was returning 0. I decided to look at the engine source, and it looks like somebody forgot to finish writing this function.

void FSteamVRHMD::GetFieldOfView(float& OutHFOVInDegrees, float& OutVFOVInDegrees) const
OutHFOVInDegrees = 0.0f;
OutVFOVInDegrees = 0.0f;

So, are there any alternate functions to get the FOV?