How to update a custom field in zoho inventory?

How to update a custom field in zoho inventory?

I have a custom field in inventory that I'm trying to update through deluge in creator but I keep getting a strange error. Here's my attempt at updating the custom field. The name of my custom field is "cf_substatus" and I noticed that it was contained within a sub-map called "custom_field_hash." Here's my attempt. 

  1. mainUpdate = Map();
  2. setStatus = package.get("custom_field_hash");
  3. setStatus.put("cf_substatus","Picked");
  4. setStatus.put("cf_substatus_unformatted","Picked");
  5. mainUpdate.put("custom_field_hash", setStatus);
  6. response = zoho.inventory.updateRecord("Packages", "829361723", packageId, mainUpdate)
  7. info response;
The error I'm getting back says "Please ensure that the custom_field_hash has less than 100 characters." Does anyone know what's going on?