docs: public static Optional<Long> toLong(Object arg) {
          if ( arg instanceof Number ) {
              return Optional.of( ( (Number) arg ).longValue() );
          }
          else if(arg instanceof String) {
              Optional<? extends Number> optional = toNumber( arg );
              if ( optional.isPresent() ) {
                  return Optional.of( optional.get().longValue() );
              }
              else {
                  return Optional.empty();
              }
          }
          else {
              return Optional.empty();
          }
      }