Content Id for Attachents through Office js Mailbox API

My team is building a Outlook Addin taskpane to generate the "current email" using the Outlook js Mailbox API in order to send it to our platform. We use Office.context.mailbox.getBodyAsync({coercionType: HTML}, ......) to get the body with inline attachments specified. In this format, inline attachments are identified by content ID (cid). 

We need a way to get the attachment content id for each attachment through the js api (it is not currently available in the Office.context.mailbox.item.attachments object), in order to add the content id to that attachment in the recreated '.eml' and match the html. We would like to keep everything client side. Is there any way to do this?

Thanks!