def delete(self, doc):
        if doc.id is None:
            raise DatabaseException('Document does not have id')
        if doc.sid is None:
            try:
                rs = self.db.docs.remove({'id': doc.id}, safe=True)
                assert rs['n'] == 1
            except Exception as e:
                raise DatabaseException(e)
            return None
        doc.data = None
        return self.update(doc)
def circle(self,x,y,r):
		for x_offset in range(-r,r+1):
			for y_offset in range(-r,r+1):
				if sqrt(x_offset**2+y_offset**2)<r:
					self.board[x+x_offset,y+y_offset] = self.color