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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def save_used_registers(self):

 """Pushes all used working registers before function call"""

        used = self.used_registers[:]
        del self.used_registers[:]
        self.used_registers_stack.append(used[:])
        used.sort()
        for reg in used:
            self.newline_text("PUSH\t%s" % SharedData.REGISTERS[reg], True)
        self.free_registers.extend(used)
        self.free_registers.sort(reverse = True)