_generate() {
    const min = this.min;
    const max = this.max;
    let timestamps = super.getDataTimestamps();
    if (!timestamps.includes(min) || !timestamps.length) {
      timestamps.splice(0, 0, min);
    }
    if (!timestamps.includes(max) || timestamps.length === 1) {
      timestamps.push(max);
    }
    return timestamps.sort((a, b) => a - b);
  }
Generates all timestamps defined in the data.
Important: this method can return ticks outside the min and max range, it's the
responsibility of the calling code to clamp values if needed.
@protected