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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 _structure_default(self, obj, cl):
 """This is the fallthrough case. Everything is a subclass of `Any`. A special condition here handles ``attrs`` classes. Bare optionals end here too (optionals with arguments are unions.) We treat bare optionals as Any. """

        if cl is Any or cl is Optional:
            return obj
        # We don't know what this is, so we complain loudly.
        msg = (
            "Unsupported type: {0}. Register a structure hook for "
            "it.".format(cl)
        )
        raise ValueError(msg)