<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def deadends(self):
 """ Get all CFGNodes that has an out-degree of 0 :return: A list of CFGNode instances :rtype: list """

        if self.graph is None:
            raise AngrCFGError('CFG hasn\'t been generated yet.')

        deadends = [i for i in self.graph if self.graph.out_degree(i) == 0]

        return deadends