<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_return_type_idx_value(self):
 """ Return the string associated to the return_type_idx :rtype: string """

        if self.return_type_idx_value == None:
            self.return_type_idx_value = self.CM.get_type(self.return_type_idx)

        return self.return_type_idx_value