function getHeatmapValue(tileValue, tilePropertyName) {
  let value;
  if (tilePropertyName === "_loadTimestamp") {
    value = JulianDate.toDate(tileValue).getTime();
  } else {
    value = tileValue;
  }
  return value;
}
Convert to a usable heatmap value (i.e. a number). Ensures that tile values that aren't stored as numbers can be used for colorization.
@private