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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 get_filename(cls):
 """ Gets filename of store on disk """

        config_home = os.environ.get("XDG_CONFIG_HOME", "~/.config")
        config_home = os.path.expanduser(config_home)

        base_path = os.path.join(config_home, "PyPump")
        if not os.path.isdir(base_path):
            os.makedirs(base_path)

        return os.path.join(base_path, "credentials.json")