code: @Override
      public String handle(Object value) {
          final StringBuilder s = new StringBuilder();
          if (value instanceof BoundingBox) {
              final BoundingBox bbox = (BoundingBox) value;
              s.append(doubleSerializer.handle(bbox.getWest())).append(',');
              s.append(doubleSerializer.handle(bbox.getNorth())).append(',');
              s.append(doubleSerializer.handle(bbox.getEast())).append(',');
              s.append(doubleSerializer.handle(bbox.getSouth()));
          } else {
              s.append(value);
          }
          return s.toString();
      }
docs: Converts the input value to a <code>left,top,right,bottom</code> string representation.
  
  @return a ltrb value
  @see fr.dudie.nominatim.client.request.paramhelper.QueryParameterSerializer#handle(java.lang.Object)