class_docstr: longest common substring similarity
      
class_docstr_tok: ["longest","common","substring","similarity"]
code: def _standart(self, s1: str, s2: str) -> str:
      matcher = _SequenceMatcher(a=s1, b=s2)
      match = matcher.find_longest_match(0, len(s1), 0, len(s2))
      return s1[match.a : match.a + match.size]
  
imports: from __future__ import annotations
  from difflib import SequenceMatcher
  from typing import Any
  from ..utils import find_ngrams
  from .base import BaseSimilarity
  from .types import TestFunc
label_desc: Use image node_id 1 for calling the LCSStr obj's underlying member method code with example usage: obj._standart(s1, s2) and returns: s1