tant in 'exp_range' scaling function:
    gamma**(cycle iterations)
scale_fn: Custom scaling policy defined by a single
    argument lambda function, where
    0 &lt;= scale_fn(x) &lt;= 1 for all x &gt;= 0.
    mode paramater is ignored
scale_mode: {'cycle', 'iterations'}.
    Defines whether scale_fn is evaluated on
    cycle number or cycle iterations (training
    iterations since start of cycle). Default is 'cycle'.
reduce_on_plateau (int): LR will be reduced after this many
                         epo