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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 normalize(self):
 """ Normalizes environment variables, paths and filters the lists of bundles to install and start. After this call, the environment variables of this process will have been updated. """

        # Add environment variables
        os.environ.update(self._environment)

        # Normalize paths and avoid duplicates
        self._paths = remove_duplicates(
            os.path.realpath(os.path.expanduser(os.path.expandvars(path)))
            for path in self._paths
            if os.path.exists(path)
        )

        # Normalize the lists of bundles
        self._bundles = remove_duplicates(self._bundles)