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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 _actual_key(self, key):
 """Translate provided key into the key used in the topology. Tries the unmodified key, the key with the default namespace, and the country converter. Raises a ``KeyError`` if none of these finds a suitable definition in ``self.topology``."""

        if key in self or key in ("RoW", "GLO"):
            return key
        elif (self.default_namespace, key) in self:
            return (self.default_namespace, key)

        if isinstance(key, str) and self.coco:
            new = coco.convert(names=[key], to='ISO2', not_found=None)
            if new in self:
                if new not in self.__seen:
                    self.__seen.add(key)
                    print("Geomatcher: Used '{}' for '{}'".format(new, key))
                return new

        raise KeyError("Can't find this location")