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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 clean(inst):
 """Routine to return VEFI data cleaned to the specified level Parameters inst : (pysat.Instrument) Instrument class object, whose attribute clean_level is used to return the desired level of data selectivity. Returns -------- Void : (NoneType) data in inst is modified in-place. Notes -------- 'dusty' or 'clean' removes data when interpolation flag is set to 1 """

    
    if (inst.clean_level == 'dusty') | (inst.clean_level == 'clean'):
        idx, = np.where(inst['B_flag'] == 0)
        inst.data = inst[idx, :]

    return None