class_docstr: Inverse square root LR scheduler.
  
  Args:
      optimizer (Optimizer): Torch optimizer.
      warmup_steps (int): Number of warmup steps.
      warmup_init_lr (tp.Optional[float]): Initial learning rate
          during warmup phase. When not set, use the provided learning rate.
code: def _get_sched_lr(self, lr: float, step: int):
      if step < self.warmup_steps:
          warmup_init_lr = self.warmup_init_lr or 0
          lr_step = (lr - warmup_init_lr) / self.warmup_steps
          lr = warmup_init_lr + step * lr_step
      return lr
  
file_path: audiocraft/audiocraft/optim/linear_warmup_lr_scheduler.py
imports: import typing
  from torch.optim import Optimizer
  from torch.optim.lr_scheduler import _LRScheduler
label_desc: Use image node_id 2 for calling the LinearWarmupLRScheduler obj's underlying member method code with example usage: obj._get_sched_lr(lr, step) and returns: lr