<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def add_returning_function(self, func_addr):
 """ Mark a function as returning. :param int func_addr: Address of the function that returns. :return: None """


        self._returning_functions.add(func_addr)
        self._updated_functions.add(func_addr)