145      * @param int $group Index group (0 for non-split, token length for split)
149     public function getTokenIndex(int $group = 0): AbstractIndex  argument
154         return new MemoryIndex($this->idxToken, $this->groupToSuffix($group), $this->isWritable);
158      * @param int $group Index group (0 for non-split, token length for split)
162     public function getFrequencyIndex(int $group = 0): AbstractIndex  argument
164 …      return new MemoryIndex($this->idxFrequency, $this->groupToSuffix($group), $this->isWritable);
192      * @param int $group
196     protected function groupToSuffix(int $group): string  argument
198         if ($group === 0 && $this->splitByLength) {
201         if ($group !== 0 && !$this->splitByLength) {
202             throw new IndexUsageException("Group $group is not valid for non-split collections");
204         return $group === 0 ? '' : (string)$group;
215      * @param int $group Index group (0 for non-split, token length for split)
219     public function resolveTokenFrequencies(int $group, array $tokenIds): array  argument
221         $freqIndex = $this->getFrequencyIndex($group);
240         foreach ($groups as $group) {
241             $freqIndex = $this->getFrequencyIndex($group);
286         foreach ($groups as $group) {
287             $freqIndex = $this->getFrequencyIndex($group);
303             $tokens = $this->getTokenIndex($group)->retrieveRows(array_keys($freqs));
345         foreach ($groups as $group) {
346             $tokenIndex = $this->getTokenIndex($group);
347             $freqIndex = $this->getFrequencyIndex($group);
353                     "Group $group: missing " .
362                     "Group $group: token count ($tc) != frequency count ($fc)"
437             $group = $this->splitByLength ? Tokenizer::tokenLength($token) : 0;
438             $groups[$group][$token] = $freq;
443         foreach ($groups as $group => $tokenFreqs) {
444             $tokenIndex = $this->getTokenIndex($group);
445             $result[$group] = [];
448                 $result[$group][$tokenId] = $freq;
538             $group = (int)(array_pop($parts) ?? 0);
539             $result[$group][$tokenId] = 0;
553         foreach ($data as $group => $tokens) {
554             $prefix = $group === 0 ? '' : "$group*";
575         foreach ($data as $group => $tokens) {
576             $freqIndex = $this->getFrequencyIndex($group);