ticks method
Returns tick values as DateTime objects.
Implementation
List<DateTime> ticks([int count = 10]) {
final d0 = _domain[0];
final d1 = _domain[1];
final span = d1.difference(d0);
// Determine appropriate interval
final interval = _selectInterval(span, count);
return _generateTicks(d0, d1, interval, count);
}