class_docstr: Smoothing helper
  http://acl2014.org/acl2014/W14-33/pdf/W14-3346.pdf
class_docstr_tok: ["Smoothing","helper","http",":","\/\/acl2014.org\/acl2014\/W14-33\/pdf\/W14-3346.pdf"]
code: def __init__(self, method: str):
      valid = ["no_smooth", "smooth1", "nltk_smooth2", "smooth2"]
      if method not in valid:
          raise ValueError(
              f"Smooth is not valid (expected: {valid}, got: {method})"
          )
      self.smooth = method
  
imports: import math
  from typing import Any, Callable, Sequence, Tuple, Union
  import torch
  from ignite.exceptions import NotComputableError
  from ignite.metrics.metric import Metric, reinit__is_reduced, sync_all_reduce
  from ignite.metrics.nlp.utils import modified_precision
label_desc: Use image node_id 1 to create a new _Smoother object  with example: obj = _Smoother(method)