code: func (hc *HeaderChain) HasHeader(hash common.Hash, number uint64) bool {
  	if hc.numberCache.Contains(hash) || hc.headerCache.Contains(hash) {
  		return true
  	}
  	return rawdb.HasHeader(hc.chainDb, hash, number)
  }
docs: // HasHeader checks if a block header is present in the database or not.