attachments: Add from another table

I have a child table in which I have an email button.  This is the script:

sendEmail({
    from: "alan@blah blah",
    to: EMAIL,
    cc: " ",
    bcc: userEmail(),
    subject: "A new Task has been added for: " + 'ASSIGNED ENGINEER' + " " + TASK.'TASK TITLE' +
    " " +
    TASK.LOCATION,
    text: "Att: " + 'ROLE PLAYER'.'FIRST NAME',
    html: TASK.'EMAIL BODY',
    attachments: file(this, "TASKS")
})

My issue is the last line.  How would I reference an attachment titled "TASKS" that is actually 'attached' to the record it is linked to?

The Table relationship is  [TASKS > ASSIGNMENTS]

When executed this script throws a crazy error which I cannot decipher.