docstr: Raises NotImplementedError error if backend choice is not implemented.
docstr_tok: ["Raises","NotImplementedError","error","if","backend","choice","is","not","implemented","."]
code: def _raise_implementation_error(self, backend: str):
      """Raises NotImplementedError error if backend choice is not implemented."""
  
      backend_list = _iter_to_str(self.backend_options.keys())
      raise NotImplementedError(
          f"{backend} backend not implemented. Use one of {backend_list} instead."
      )
  
file_path: alibi-detect/alibi_detect/utils/frameworks.py
imports: from .missing_optional_dependency import ERROR_TYPES
  from typing import Optional, List, Dict, Iterable
  from enum import Enum
label_desc: Use image node_id 4 for calling the BackendValidator obj's underlying member method code with example usage: obj._raise_implementation_error(backend) without return types