docs: @Pure
  	public int getPointCountInGroup(int groupIndex) {
  		if (groupIndex == 0 && this.pointCoordinates == null) {
  			return 0;
  		}
  		final int firstInGroup = firstInGroup(groupIndex);
  		final int lastInGroup = lastInGroup(groupIndex);
  		return (lastInGroup - firstInGroup) / 2 + 1;
  	}