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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 _from_dict(cls, mapping):
 """Create an instance from the corresponding state mapping. :type mapping: dict :param mapping: the instance state. """

        if mapping.get("all"):
            return cls(all_=True)

        r_mappings = mapping.get("ranges", ())
        ranges = [KeyRange(**r_mapping) for r_mapping in r_mappings]

        return cls(keys=mapping.get("keys", ()), ranges=ranges)