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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 all_keys(self, uppercase_keys=False):
 """Return all keys regardless where they are set."""

        d = {}

        for k in self._override.keys():
            d[k.upper() if uppercase_keys else k.lower()] = {}

        for k in self._args.keys():
            d[k.upper() if uppercase_keys else k.lower()] = {}

        for k in self._env.keys():
            d[k.upper() if uppercase_keys else k.lower()] = {}

        for k in self._config.keys():
            d[k.upper() if uppercase_keys else k.lower()] = {}

        for k in self._kvstore.keys():
            d[k.upper() if uppercase_keys else k.lower()] = {}

        for k in self._defaults.keys():
            d[k.upper() if uppercase_keys else k.lower()] = {}

        for k in self._aliases.keys():
            d[k.upper() if uppercase_keys else k.lower()] = {}

        return d.keys()