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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_var_name(nc):
 """Guesses the variable_name of an open NetCDF file """


    non_variable_names = [
        'lat',
        'lat_bnds',
        'lon',
        'lon_bnds',
        'time',
        'latitude',
        'longitude',
        'bnds'
    ]

    _vars = set(nc.variables.keys())
    _vars.difference_update(set(non_variable_names))
    if len(_vars) == 1:
        return _vars.pop()
    return None