public function ensureCountIndex(array $fields, $includeRunning)
{
if (!is_bool($includeRunning)) {
throw new \InvalidArgumentException('$includeRunning was not a boolean');
}
$completeFields = [];
if ($includeRunning) {
$completeFields['running'] = 1;
}
self::verifySort($fields, 'fields', $completeFields);
$this->ensureIndex($completeFields);
}