detectOutsideLabelCollision method
Detects whether the current outside label collides with the previous label.
Implementation
@override
bool detectOutsideLabelCollision(num labelY, bool labelLeftOfChart,
    num? previousOutsideLabelY, bool? previousLabelLeftOfChart) {
  if (!extendLeaderLine) {
    return super.detectOutsideLabelCollision(labelY, labelLeftOfChart,
        previousOutsideLabelY, previousLabelLeftOfChart);
  } else {
    return _collisionDetectionParams.any((param) => super
        .detectOutsideLabelCollision(labelY, labelLeftOfChart,
            param.previousOutsideLabelY, param.previousLabelLeftOfChart));
  }
}