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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 mapping(self):
 """Get a mapping class for this model This method will return a Mapping class for your model, generating it using settings from a `Mapping` class on your model (if one exists). The generated class is cached on the manager. """

        if not hasattr(self, "_mapping"):
            if hasattr(self.model, "Mapping"):
                mapping_klass = type("Mapping", (DjangoMapping, self.model.Mapping), {})
            else:
                mapping_klass = get_first_mapping(self.model)
                if mapping_klass is None:
                    mapping_klass = DjangoMapping
            self._mapping = mapping_klass(self.model)
        return self._mapping