function typeToLane(d) {
  switch (d.type) {
    case CODE_PAGE:
      return 0;
    case REACHED_PAGE:
      return 1;
    case RESIDENCY:
      return 2;
  }
}
/**
 * @return {int} the lane index for a given data item.
 */
@return {int} the lane index for a given data item.
@return { int } the lane index for a given data item .
function typeToLane(d) {
  switch (d.type) {
    case CODE_PAGE:
      return 0;
    case REACHED_PAGE:
      return 1;
    case RESIDENCY:
      return 2;
  }
}
function typeToLane ( d ) { switch ( d . type ) { case CODE_PAGE : return 0 ; case REACHED_PAGE : return 1 ; case RESIDENCY : return 2 ; } }
@return {int} the lane index for a given data item.
@return { int } the lane index for a given data item .