code: function fadeLinesBut(exceptionItemId) {
              let classToFade = 'g.legend-entry';
              let entryLine = svg.select(`[data-item="${exceptionItemId}"]`);
  
              if (entryLine.nodes().length){
                  svg.select('.legend-group')
                      .selectAll(classToFade)
                      .classed(isFadedClassName, true);
  
                  entryLine.classed(isFadedClassName, false);
              }
          }
docs: Applies the faded class to all lines but the one that has the given id
  @param  {number} exceptionItemId Id of the line that needs to stay the same
  @private