class_docstr: An abstract class that represents constraints which are applied before
  the transformation.
  
  These restrict which words are allowed to be modified during the
  transformation. For example, we might not allow stopwords to be
  modified.
docstr: Set the extra representation of the constraint using these keys.
  
  To print customized extra information, you should reimplement
  this method in your own constraint. Both single-line and multi-
  line strings are acceptable.
code: def extra_repr_keys(self):
      """Set the extra representation of the constraint using these keys.
  
      To print customized extra information, you should reimplement
      this method in your own constraint. Both single-line and multi-
      line strings are acceptable.
      """
      return []
  
file_path: TextAttack/textattack/constraints/pre_transformation_constraint.py
imports: from abc import ABC, abstractmethod
  from textattack.shared.utils import ReprMixin
label_desc: Use image node_id 4 for calling the PreTransformationConstraint obj's underlying member method code with example usage: obj.extra_repr_keys() and returns: list