code: def _get_structural_id(
      node: PipelineNode, fold_id: Optional[int] = None
  ) -> str:
      """
      Gets unique id from node.
  
      :param node: node to get uid from
      :param fold_id: fold number to fit data
      :return structural_id: unique node identificator
      """
      structural_id = node.descriptive_id
      structural_id += f"_{fold_id}" if fold_id is not None else ""
      return structural_id
  
file_path: FEDOT/fedot/core/caching/pipelines_cache.py
imports: import sqlite3
  from typing import List, Optional, TYPE_CHECKING, Union
  from golem.utilities.data_structures import ensure_wrapped_in_sequence
  from fedot.core.caching.base_cache import BaseCache
  from fedot.core.caching.pipelines_cache_db import OperationsCacheDB
  from fedot.core.pipelines.node import PipelineNode
label_desc: Use image node_id 1 for calling a global function with example usage: _get_structural_id(node, fold_id) and returns: structural_id