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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 arch_size(self):
 """Return the architecure size in bits."""

        if not self._ptr:
            raise BfdException("BFD not initialized")

        try:
            return _bfd.get_arch_size(self._ptr)
        except Exception, err:
            raise BfdException("Unable to determine architeure size.")