code: func (r Billing_Invoice) EmailInvoices(options *datatypes.Container_Billing_Invoice_Email) (err error) {
  	var resp datatypes.Void
  	params := []interface{}{
  		options,
  	}
  	err = r.Session.DoRequest("SoftLayer_Billing_Invoice", "emailInvoices", params, &r.Options, &resp)
  	return
  }
docs: // Create a transaction to email PDF and/or Excel invoice links to the requesting user's email address. You must have a PDF reader installed in order to view these files.