'Remove a record from the deduplicate list
@param r: the S3Request
@param attr: the controller parameters for the request'

def unmark(self, r, **attr):

    s3 = current.session.s3
    DEDUPLICATE = self.DEDUPLICATE
    success = current.xml.json_message()
    if (DEDUPLICATE not in s3):
        return success
    else:
        bookmarks = s3[DEDUPLICATE]
    tablename = self.tablename
    if (tablename not in bookmarks):
        return success
    else:
        records = bookmarks[tablename]
    record_id = str(self.record_id)
    if record_id:
        if (record_id in records):
            records.remove(record_id)
        if (not records):
            bookmarks.pop(tablename)
    else:
        bookmarks.pop(tablename)
    return success
