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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 prepareSystem(cls):
 """ Prepares this system for the downloading and lookup of resources. This method should only be invoked on a worker node. It is idempotent but not thread-safe. """

        try:
            resourceRootDirPath = os.environ[cls.rootDirPathEnvName]
        except KeyError:
            # Create directory holding local copies of requested resources ...
            resourceRootDirPath = mkdtemp()
            # .. and register its location in an environment variable such that child processes
            # can find it.
            os.environ[cls.rootDirPathEnvName] = resourceRootDirPath
        assert os.path.isdir(resourceRootDirPath)