class_docstr: Warmup + InverseSqrt decay scheduler.
  
  Args:
      noam_warmup (int): number of warmup iterations.
class_docstr_tok: ["Warmup","+","InverseSqrt","decay","scheduler",".","Args",":","noam_warmup","(","int",")",":","number","of","warmup","iterations","."]
docstr: Scale of lr.
docstr_tok: ["Scale","of","lr","."]
code: def scale(self, step):
      """Scale of lr."""
      step += 1  # because step starts from 0
      return self.normalize * min(
          step**-0.5, step * self.warmup**-1.5
      )
  
imports: import argparse
  from espnet.utils.dynamic_import import dynamic_import
  from espnet.utils.fill_missing_args import fill_missing_args
label_desc: Use image node_id 3 for calling the NoamScheduler obj's underlying member method code with example usage: obj.scale(step) and returns: unknown