code: func NewCfIndex(db database.DB, chainParams *chaincfg.Params) *CfIndex {
  	return &CfIndex{db: db, chainParams: chainParams}
  }
docs: // NewCfIndex returns a new instance of an indexer that is used to create a
  // mapping of the hashes of all blocks in the blockchain to their respective
  // committed filters.
  //
  // It implements the Indexer interface which plugs into the IndexManager that
  // in turn is used by the blockchain package. This allows the index to be
  // seamlessly maintained along with the chain.