Pulling Excel.xlsx workbook from Sharepoint site using Microsoft Graph API

As stated in the title, I've been trying to use the Microsoft Graph API to pull an Excel workbook from our company's Sharepoint site. I am able to retrieve the metadata for the file, but when I add the /workbook/ segment to the URL, I receive the below error:

{
  "error": {
    "code": "BadRequest",
    "message": "Resource not found for the segment 'workbook'.",
    "innerError": {
      "request-id": "bf41e41a-bc01-4c3b-b1d7-3125c4d48124",
      "date": "2019-04-10T16:29:07"
    }
  }
}

Here is what the successful call getting the file metadata looks like:

https://graph.microsoft.com/v1.0/sites/{siteid}/lists/{listid}/items/273

And here is the call I am making which returns the above error:

https://graph.microsoft.com/v1.0/sites/{siteid}/lists/{listid}/items/273/workbook/

I was able to find this stackoverflow post discussing a similar error, however that was a couple of years ago, apparently using a beta version of the Graph API, and I was not able to get any farther using suggestions from that post. Get workbook from sharepoint site using microsoft graph beta

I am building my request URL based on reading these two Microsoft docs: https://learn.microsoft.com/en-us/graph/api/resources/sharepoint?view=graph-rest-1.0 https://learn.microsoft.com/en-us/graph/api/resources/excel?view=graph-rest-1.0

I don't think it's relevant, but I'm using C# and building the requests with Restsharp.

Does anyone have any insight on this?
Thanks!