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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 config(self):
 """Get the complete configuration where the default, config, environment, and override values are merged together. Returns: (DotDict):
 A dictionary of configuration values that allows lookups using dot notation. """

        if self._full_config is None:
            self._full_config = DotDict()
            self._full_config.merge(self._default)
            self._full_config.merge(self._config)
            self._full_config.merge(self._environment)
            self._full_config.merge(self._override)
        return self._full_config