Return a thread-safe, concurrent set.
Return a new set of value type string, containing the specified items.
string
items
{@link com.sap.cloud.mobile.kotlin.odata.StringSet#of(kotlin.String...) StringSet.of}.
{@link com.sap.cloud.mobile.kotlin.odata.StringSet#from(com.sap.cloud.mobile.kotlin.odata.StringList) StringSet.from}.