erations per
            half cycle. Authors suggest setting step_size
            2-8 x training iterations in epoch.
        mode: one of {triangular, triangular2, exp_range}.
            Default &#39;triangular&#39;.
            Values correspond to policies detailed above.
            If scale_fn is not None, this argument is ignored.
        gamma: constant in &#39;exp_range&#39; scaling function:
            gamma**(cycle iterations)
        scale_fn: Custom scaling policy defined by a single
        