class_docstr: Runing statistics for counting tokens before/after subword transform.
code: def __str__(self) -> str:
      return "{}: {} -> {} tokens".format(
          self.name(), self.words, self.subwords
      )
  
imports: import re
  from onmt.utils.logging import logger
  from onmt.transforms import register_transform
  from .transform import Transform, ObservableStats
  from onmt.constants import DefaultTokens
label_desc: Use image node_id 3 for calling the SubwordStats obj's underlying member method code with example usage: obj.__str__() and returns: str