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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 setup_environment():
 """Ensures that the environmental variable RAFCON_LIB_PATH is existent """

    try:
        from gi.repository import GLib
        user_data_folder = GLib.get_user_data_dir()
    except ImportError:
        user_data_folder = join(os.path.expanduser("~"), ".local", "share")
    rafcon_root_path = dirname(realpath(rafcon.__file__))
    user_library_folder = join(user_data_folder, "rafcon", "libraries")

    # The RAFCON_LIB_PATH points to a path with common RAFCON libraries
    # If the env variable is not set, we have to determine it. In the future, this should always be
    # ~/.local/share/rafcon/libraries, but for backward compatibility, also a relative RAFCON path is supported
    if not os.environ.get('RAFCON_LIB_PATH', None):
        if exists(user_library_folder):
            os.environ['RAFCON_LIB_PATH'] = user_library_folder
        else:
            os.environ['RAFCON_LIB_PATH'] = join(dirname(dirname(rafcon_root_path)), 'share', 'libraries')

    # Install dummy _ builtin function in case i18.setup_l10n() is not called
    if sys.version_info >= (3,):
        import builtins as builtins23
    else:
        import __builtin__ as builtins23
    if "_" not in builtins23.__dict__:
        builtins23.__dict__["_"] = lambda s: s