Saves this feature collection back to the item it originated from.
The feature collection must have a valid FeatureCollection.item property and if the operation was successful the item will be updated with the feature collection. A feature collection has a valid item property if it was created using FeatureCollection.FeatureCollection(Item) or has been previously saved as a new item.
a Result indicating whether the feature collection was successfully saved. The result will be a failure with type: