code: function getMaxY() {
      if (self.options.maxY) {
        return self.options.maxY;
      }
  
      var max = -Infinity;
  
      for(let i = 0; i < data.length; i++) {
        if (data[i].y.length) {
          var current = _.max(data[i].y, parseFloat);
          if (current > max) {
            max = current;
          }
        }
      }
  
      return max + (max - self.options.minY) * 0.2;
    }
docs: iteratee for lodash _.max