(* ::Package:: *)
values = "
/* Keyword value */
line-height: normal;
/* Unitless values: use this number multiplied
by the element's font size */
line-height: 3.5;
/* <length> values */
line-height: 3em;
/* <percentage> values */
line-height: 34%;
/* Global values */
line-height: inherit;
line-height: initial;
line-height: revert;
line-height: revert-layer;
line-height: unset;
";
all = Sort@StringCases[
values,
RegularExpression[":\\s*([a-zA-Z0-9-]+);"] :> "$1"
];
"[\"" <> StringRiffle[all, "\",\""] <> "\"].contains(&mode)"