code: func (idx *AddrIndex) Create(dbTx database.Tx) error {
  	_, err := dbTx.Metadata().CreateBucket(addrIndexKey)
  	return err
  }
docs: // Create is invoked when the indexer manager determines the index needs
  // to be created for the first time.  It creates the bucket for the address
  // index.
  //
  // This is part of the Indexer interface.