class_docstr: This is an abstract class that contains main helper functionality for
  search methods.
  
  A search method is a strategy for applying transformations until the
  goal is met or the search is exhausted.
docstr: Perturbs `attacked_text` from ``initial_result`` until goal is
  reached or search is exhausted.
  
  Must be overridden by specific search methods.
code: def perform_search(self, initial_result):
      """Perturbs `attacked_text` from ``initial_result`` until goal is
      reached or search is exhausted.
  
      Must be overridden by specific search methods.
      """
      raise NotImplementedError()
  
file_path: TextAttack/textattack/search_methods/search_method.py
imports: from abc import ABC, abstractmethod
  from textattack.shared.utils import ReprMixin
label_desc: Use image node_id 2 for calling the SearchMethod obj's underlying member method code with example usage: obj.perform_search(initial_result) without return types