What does this mean '%iff%'? ( split.by %iff% "none" exists in FeaturePlot function)

[khl0798]

I want to get the genes expression tsne figure by FeaturePlot function ( which use GetAssayData to get genes expressions values., GetAssayData get gene expression by assay=integrated value default unless you set assay param.)

I want to get genes expression tsne figure by assay=RNA in GetAssayData function.
I I looked up the source code and came across this symbol: %iff%, what does this mean?

[khl0798]

%iff% <- function(lhs, rhs) {
if (!is.null(x = lhs)) {
return(rhs)
} else {
return(lhs)
}
}