How to reference an existing parent document in CSV to Docs

I need upload a new list of CHWs using cht csv-to-docs but these need to be attached to a hospital in the hierarchy that already exists in couchdb upstream. What is the recommended way of referencing the already existing parent document in the CSV.

If you put the UUID of the parent (hospital) under column parent._id, it should work.

Thanks @binod, I see that I can also build a deeper doc using a chain e.g having 2 columns like parent._id, parent.parent._id builds a nice doc as

"parent": {
    "_id": "parent_id",
    "parent": {
      "_id": "parent_parent_id"
    }
  },