class_docstr: The PiecewiseLinearWarmupLR scheduler
  
  This scheduler is similar to WarmupLR Scheduler except that
  the warmup stage is piecewise linear.
code: def get_lr(self):
      step_num = self.last_epoch + 1
      return [
          np.interp(
              step_num,
              self.warmup_steps_list,
              self.warmup_lr_list,
              right=lr
              * self.warmup_steps_list[-1] ** 0.5
              * step_num**-0.5,
          )
          for lr in self.base_lrs
      ]
  
file_path: espnet/espnet2/schedulers/piecewise_linear_warmup_lr.py
imports: from typing import List, Union
  import numpy
  import torch
  from torch.optim.lr_scheduler import _LRScheduler
  from typeguard import check_argument_types
  from espnet2.schedulers.abs_scheduler import AbsBatchStepScheduler
label_desc: Use image node_id 3 for calling the PiecewiseLinearWarmupLR obj's underlying member method code with example usage: obj.get_lr() and returns: unknown