code: func (db *DB) Put(key, value []byte, wo *opt.WriteOptions) error {
  	return db.putRec(keyTypeVal, key, value, wo)
  }
docs: // Put sets the value for the given key. It overwrites any previous value
  // for that key; a DB is not a multi-map. Write merge also applies for Put, see
  // Write.
  //
  // It is safe to modify the contents of the arguments after Put returns but not
  // before.