public Boolean IsProperSubsetOf([NotNull] IEnumerable <T> other)
{
if (other is null)
{
throw new ArgumentNullException(nameof(other));
}
return(other switch
{
ISet <T> set => set.IsProperSupersetOf(this),
IImmutableSet <T> set => set.IsProperSupersetOf(this),
IReadOnlySet <T> set => set.IsProperSupersetOf(this),
_ => other.ToHashSet().IsProperSupersetOf(this)
});
public bool IsProperSupersetOf(IEnumerable <string> other) => _data.IsProperSupersetOf(other);
