class_docstr: Contractions.
  Replaces each expansion with its contracted version.
  
  Perturbation example:
  
  **Input:**
      She is a doctor, and I am a student
  
  **Output:**
      She's a doctor, and I'm a student
code: def description(self) -> PerturbationDescription:
      return PerturbationDescription(name=self.name, robustness=True)
  
file_path: H2O/h2o_hf/helm/src/helm/benchmark/augmentations/contraction_expansion_perturbation.py
imports: from typing import Dict
  import re
  from random import Random
  from helm.common.general import match_case
  from .perturbation import Perturbation
  from .perturbation_description import PerturbationDescription
label_desc: Use image node_id 2 for calling the ContractionPerturbation obj's underlying member method code with example usage: obj.description() and returns: PerturbationDescription