src/Russian/RussianLanguage.php
public static function isPaired($consonant)
    {
        $consonant = S::lower($consonant);
        return array_key_exists($consonant, static::$pairs) || (array_search($consonant, static::$pairs) !== false);
    }
public static function isPaired($consonant)
    {
        $consonant = S::lower($consonant);
        return array_key_exists($consonant, static::$pairs) || (array_search($consonant, static::$pairs) !== false);
    }
Проверка парности согласной

@param $consonant
@return bool