public function distanceMultiplier($distanceMultiplier)
{
if ($this->query['type'] !== Query::TYPE_GEO_NEAR) {
throw new BadMethodCallException('This method requires a geoNear command (call geoNear() first)');
}
$this->query['geoNear']['options']['distanceMultiplier'] = $distanceMultiplier;
return $this;
}