code: func (f *FilterHeaderStore) ChainTip() (*chainhash.Hash, uint32, error) {
  	// Lock store for read.
  	f.mtx.RLock()
  	defer f.mtx.RUnlock()
  
  	_, tipHeight, err := f.chainTip()
  	if err != nil {
  		return nil, 0, fmt.Errorf("unable to fetch chain tip: %v", err)
  	}
  
  	latestHeader, err := f.readHeader(tipHeight)
  	if err != nil {
  		return nil, 0, fmt.Errorf("unable to read header: %v", err)
  	}
  
  	return latestHeader, tipHeight, nil
  }
docs: // ChainTip returns the latest filter header and height known to the
  // FilterHeaderStore.