Returns a new series with an index containing the specified keys. When the key is not found in the current series, the newly returned series will contain a missing value. When the second parameter is not specified, the keys have to exactly match the keys in the current series (`Lookup.Exact`). ## Parameters * `keys` - A collection of keys in the current series. [category:Accessors and slicing]

Returns a new series with an index containing the specified keys. When the key is not found in the current series, the newly returned series will contain a missing value. When the second parameter is not specified, the keys have to exactly match the keys in the current series (`Lookup.Exact`). ## Parameters * `keys` - A collection of keys in the current series. * `lookup` - Specifies the lookup behavior when searching for keys in the current series. `Lookup.NearestGreater` and `Lookup.NearestSmaller` can be used when the current series is ordered. [category:Accessors and slicing]