Type Alias ExcludeKeys<T, U, Mode>

ExcludeKeys: {
    [P in keyof T]-?: Mode extends "normal"
        ? T[P] extends U ? never : P
        : U extends T[P] ? never : P
}[keyof T]

From T, construct a union of the keys which are not assignable to U

T
U
Mode extends "normal" | "invert" = "normal"
If set to 'invert', will use keys to which U is not assignable