code: public function set($id, $data, $lifetime = NULL) {
          if ($lifetime === NULL) {
              $lifetime = $this->default_expire;
          }
  
          return \apcu_store($this->_sanitize_id($id), $data, $lifetime);
      }
docs: Set a value to cache with id and lifetime
  
  $data = 'bar';
  
  // Set 'bar' to 'foo' in apc group, using default expiry
  Cache::instance('apc')->set('foo', $data);
  
  // Set 'bar' to 'foo' in apc group for 30 seconds
  Cache::instance('apc')->set('foo', $data, 30);
  
  @param   string $id id of cache entry
  @param   string $data data to set to cache
  @param   integer $lifetime lifetime in seconds
  @return  boolean