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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 _check_list_props(self, inst: "InstanceNode") -> None: """Check uniqueness of keys and "unique" properties, if applicable."""

        if self.keys:
            self._check_keys(inst)
        for u in self.unique:
            self._check_unique(u, inst)