code: func (b *Bucket) free() {
  	if b.root == 0 {
  		return
  	}
  
  	var tx = b.tx
  	b.forEachPageNode(func(p *page, n *node, _ int) {
  		if p != nil {
  			tx.db.freelist.free(tx.meta.txid, p)
  		} else {
  			n.free()
  		}
  	})
  	b.root = 0
  }
docs: // free recursively frees all pages in the bucket.