docs: public static Optional<Number> abs( Object arg ) {
          if(arg instanceof Integer) {
              return Optional.<Number>of( java.lang.Math.abs( (Integer) arg ));
          }
          else if(arg instanceof Double) {
              return Optional.<Number>of( java.lang.Math.abs( (Double) arg ));
          }
          else if(arg instanceof Long) {
              return Optional.<Number>of( java.lang.Math.abs( (Long) arg ));
          }
          else if(arg instanceof String) {
              return abs( Objects.toNumber( arg ).get() );
          }
          return Optional.empty();
      }