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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 _setup_arch(self, arch_mode=None):
 """Set up architecture. """

        # set up architecture information
        self.arch_info = None

        if self.binary.architecture == ARCH_X86:
            self._setup_x86_arch(arch_mode)
        else:
            # TODO: add arch to the binary file class.
            self._setup_arm_arch(arch_mode)