code: func NewLevelDBDatabase(file string, cache int, handles int, namespace string) (ethdb.Database, error) {
  	db, err := leveldb.New(file, cache, handles, namespace)
  	if err != nil {
  		return nil, err
  	}
  	return NewDatabase(db), nil
  }
docs: // NewLevelDBDatabase creates a persistent key-value database without a freezer
  // moving immutable chain segments into cold storage.