microsoft graph api for sharepoint to access list item attachment web url

i am using ms graph beta APIS to access sharepoint online. The current GET to get a list with its list items is like below

https://graph.microsoft.com/beta/sites/mytenant.sharepoint.com:/sites/mysite:/lists/mylist?select=id,name,lastModifiedDateTime&expand=items(expand=fields(select=Title,Attachments,OptyNumber))

this works great and return me Title,Attachments,OptyNumber. Now, the list may have attachments and i need the weburl of the attachments. How do i do that?

Trying like https://graph.microsoft.com/beta/sites/mytenant.sharepoint.com:/sites/mysite:/lists/mylist:/attachments

throws error {     "error": {         "code": "BadRequest",         "message": "Only one path can be specified in the URL.",         "innerError": {             "request-id": "f9e94fee-082f-45af-a777-2e1d3debb99c",             "date": "2018-11-09T03:52:32"         }     } } 

which makes sense to me. so how do i get the associated attachment url with each of the list item if its there