docs: function shouldUseZoomLevel(zoomLevel) {
                  var similarity = lastZoomLevel / zoomLevel;
                  // remove duplicates
                  if (zoomLevel === lastZoomLevel) {
                      return false;
                  }
                  // keep anything that is within the similarity threshold
                  if (similarity < ZOOM_LEVEL_SIMILARITY_THRESHOLD) {
                      return true;
                  }
                  // check if it's a preset
                  if (util.inArray(zoomLevel, presets) > -1) {
                      // keep presets if they are within a higher threshold
                      if (similarity < ZOOM_LEVEL_PRESETS_SIMILARITY_THRESHOLD) {
                          return true;
                      }
                  }
                  return false;
              }