Auto conversion from/to pxr::VtValue We define a GetUsdValue() instead of `operator pxr::VtValue&_ because pxr::VtValue itself has lower precedence, implicit generic conversions and operators that can conflict/generate hidden bugs if we try using them without having this header included (e.g. we could end up with a pxr::VtValue containing anUE::FVtValueinstead)