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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_default_config_file_path(init_filename=None):
 """gets the path to the default config-file"""

    prm_dir = get_package_prm_dir()
    if not init_filename:
        init_filename = DEFAULT_FILENAME
    src = os.path.join(prm_dir, init_filename)
    return src