presto-main/src/main/java/io/prestosql/metadata/Signature.java/Signature/unmangleOperator
class Signature:    @VisibleForTesting
    public static OperatorType unmangleOperator(String mangledName)
    {
        checkArgument(mangledName.startsWith(OPERATOR_PREFIX), "not a mangled operator name: %s", mangledName);
        return OperatorType.valueOf(mangledName.substring(OPERATOR_PREFIX.length()));
    }