def get_next_id(self):
        try:
            query = {'_id': 'last_id'}
            update = {'$inc': {'id': 1}}
            fn = self.db.internal.find_and_modify
            row = fn(query, update, upsert=True, new=True)
        except Exception as e:
            raise DatabaseException(e)
        return row['id']
def __init__(self, w, h, color = "empty"):
		self.board = zeros((h,w), dtype=uint8)
		self.w = w
		self.h = h
		self.set_brush(color)