Saving the groups generated from groupby operation #5674

Problem
Group by is an expensive operation. Therefore I want to store my dataset to disk in the form of groups from group by operation. My use case is concerned with the groups, for example I want to take advantage of the lazy loading and only want to load selected groups into memory and process them.

Preferred Solution

• An additional parameter to pass the groups to cache when writing the dataset to disk
  Or
• A separate function to write the dataset as a collection of groups to file.

Alternatives considered
Treating each group as separate dataset and writing each of them to separate file. This is not suitable if number of groups is large and each group is relatively very small.

Additional context
It would also be great if groupby operation is natively supported for multiple coordinates.