def get_last_tid(self):
        try:
            spec = {'tid': {'$gt': 0}}
            sort = [('tid', -1)]
            row = self.db.docs.find_one(spec, sort=sort)
        except Exception as e:
            raise DatabaseException(e)
        if row:
            return row['tid']
        return 0
def linear_search(lst,size,value):
    i = 0
    while i < size:
        if lst[i] == value:
            return i
        i = i + 1
    return -1