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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 prg_rom(self):
 """Return the PRG ROM of the ROM file."""

        try:
            return self.raw_data[self.prg_rom_start:self.prg_rom_stop]
        except IndexError:
            raise ValueError('failed to read PRG-ROM on ROM.')