<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def full_tasktrace(self):
 """ List of all failed tasks caused by this and all previous errors. Returns: List[Task] """

        if self.prev_error:
            return self.prev_error.tasktrace + self.tasktrace
        else:
            return self.tasktrace