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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 _mode(self, s):
 """Check file mode format and parse into an int. :return: mode as integer """

        # Note: Output from git-fast-export slightly different to spec
        if s in [b'644', b'100644', b'0100644']:
            return 0o100644
        elif s in [b'755', b'100755', b'0100755']:
            return 0o100755
        elif s in [b'040000', b'0040000']:
            return 0o40000
        elif s in [b'120000', b'0120000']:
            return 0o120000
        elif s in [b'160000', b'0160000']:
            return 0o160000
        else:
            self.abort(errors.BadFormat, 'filemodify', 'mode', s)