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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 set_vml_accuracy_mode(mode):
 """ Set the accuracy mode for VML operations. The `mode` parameter can take the values: - 'high': high accuracy mode (HA), <1 least significant bit - 'low': low accuracy mode (LA), typically 1-2 least significant bits - 'fast': enhanced performance mode (EP) - None: mode settings are ignored This call is equivalent to the `vmlSetMode()` in the VML library. See: http://www.intel.com/software/products/mkl/docs/webhelp/vml/vml_DataTypesAccuracyModes.html for more info on the accuracy modes. Returns old accuracy settings. """

    if use_vml:
        acc_dict = {None: 0, 'low': 1, 'high': 2, 'fast': 3}
        acc_reverse_dict = {1: 'low', 2: 'high', 3: 'fast'}
        if mode not in acc_dict.keys():
            raise ValueError(
                "mode argument must be one of: None, 'high', 'low', 'fast'")
        retval = _set_vml_accuracy_mode(acc_dict.get(mode, 0))
        return acc_reverse_dict.get(retval)
    else:
        return None