Turn off Identity Method via API

We're running into some trouble setting the identity_method = "none" so that
we can remove the double confirmation. We really don't want our users having to confirm by email or SMS. 

This is our request to send_document API endpoint:

{
name: 'Document Name',
expires_in: 300,
roles: [{
name: 'Member',
signer_email: 'signer@email.com',
signer_name: 'John Smith',
}],
callback_url: 'https://oururl.com/callback',
identity_method: 'none'
}

The response is a 401 error message,
api.rightsignature.com/v1/session_credentials/current Failed to load
resource: the server responded with a status of 401 (Unauthorized)

Are you able to provide some guidance here? 

I know that in the RightSignature Web UI it's possible to set the document's identity_method to "none."