(* ::Package:: *)
values = "
/* Keyword values */
flex-basis: auto;
/* Intrinsic sizing keywords */
flex-basis: fill;
flex-basis: max-content;
flex-basis: min-content;
flex-basis: fit-content;
/* Automatically size based on the flex item's content */
flex-basis: content;
/* Global values */
flex-basis: inherit;
flex-basis: initial;
flex-basis: revert;
flex-basis: unset;
";
all = Sort@StringCases[
values,
RegularExpression[":\\s*([a-zA-Z0-9-]+);"] :> "$1"
];
"[\"" <> StringRiffle[all, "\",\""] <> "\"].contains(&mode)"