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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_srtm_dir(self):
 """ The default path to store files. """

        # Local cache path:
        result = ""
        if 'HOME' in mod_os.environ:
            result = mod_os.sep.join([mod_os.environ['HOME'], '.cache', 'srtm'])
        elif 'HOMEPATH' in mod_os.environ:
            result = mod_os.sep.join([mod_os.environ['HOMEPATH'], '.cache', 'srtm'])
        else:
            raise Exception('No default HOME directory found, please specify a path where to store files')

        if not mod_path.exists(result):
            mod_os.makedirs(result)

        return result