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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 as_spinmode(cls, obj):
 """Converts obj into a `SpinMode` instance"""

        if isinstance(obj, cls):
            return obj
        else:
            # Assume a string with mode
            try:
                return _mode2spinvars[obj]
            except KeyError:
                raise KeyError("Wrong value for spin_mode: %s" % str(obj))