fun getAttachment(index: Int): Attachment
Helper to simplify getting an indexed attachment.
index - the position of the item in the attachments.
Return
The Attachment at the requested index.
fun getAttachment(id: SecureHash): Attachment
Helper to simplify getting an indexed attachment.
id - the SecureHash of the desired attachment.
IllegalArgumentException - if no item matches the id.
Return
The Attachment with the matching id.