function tickValues(scale, count) {
    return scale.bins ? validTicks(scale, scale.bins, count) : scale.ticks ? scale.ticks(count) : scale.domain();
  }
Generate tick values for the given scale and approximate tick count or
interval value. If the scale has a 'ticks' method, it will be used to
generate the ticks, with the count argument passed as a parameter. If the
scale lacks a 'ticks' method, the full scale domain will be returned.
@param {Scale} scale - The scale for which to generate tick values.
@param {*} [count] - The approximate number of desired ticks.
@return {Array<*>} - The generated tick values.