140      * @param int $group Index group (0 for non-split, token length for split)
144     public function getTokenIndex(int $group = 0): AbstractIndex  argument
149         return new MemoryIndex($this->idxToken, $this->groupToSuffix($group), $this->isWritable);
153      * @param int $group Index group (0 for non-split, token length for split)
157     public function getFrequencyIndex(int $group = 0): AbstractIndex  argument
159 …      return new MemoryIndex($this->idxFrequency, $this->groupToSuffix($group), $this->isWritable);
187      * @param int $group
191     protected function groupToSuffix(int $group): string  argument
193         if ($group === 0 && $this->splitByLength) {
196         if ($group !== 0 && !$this->splitByLength) {
197             throw new IndexUsageException("Group $group is not valid for non-split collections");
199         return $group === 0 ? '' : (string)$group;
210      * @param int $group Index group (0 for non-split, token length for split)
214     public function resolveTokenFrequencies(int $group, array $tokenIds): array  argument
216         $freqIndex = $this->getFrequencyIndex($group);
235         foreach ($groups as $group) {
236             $freqIndex = $this->getFrequencyIndex($group);
278         foreach ($groups as $group) {
279             $tokenIndex = $this->getTokenIndex($group);
280             $freqIndex = $this->getFrequencyIndex($group);
286                     "Group $group: missing " .
295                     "Group $group: token count ($tc) != frequency count ($fc)"
370             $group = $this->splitByLength ? Tokenizer::tokenLength($token) : 0;
371             $groups[$group][$token] = $freq;
376         foreach ($groups as $group => $tokenFreqs) {
377             $tokenIndex = $this->getTokenIndex($group);
378             $result[$group] = [];
381                 $result[$group][$tokenId] = $freq;
471             $group = (int)(array_pop($parts) ?? 0);
472             $result[$group][$tokenId] = 0;
486         foreach ($data as $group => $tokens) {
487             $prefix = $group === 0 ? '' : "$group*";
508         foreach ($data as $group => $tokens) {
509             $freqIndex = $this->getFrequencyIndex($group);