code: def build(self, key: str) -> Any:
      if key not in self.config:
          raise KeyError()
      if key in self.builds_started:
          raise LoopInConfigError(key)
      self.builds_started.append(key)
      self.experiment[key] = self.builder.instantiate(
          self.config[key], name=key
      )
      return self.experiment[key]
  
imports: import logging
  import os
  import traceback
  from abc import ABCMeta, abstractmethod
  from pathlib import Path
  from typing import Any, Callable, Dict, List, Mapping, Type, Union
  import toml
  import yaml
label_desc: Use image node_id 4 for calling the ExperimentConfig obj's underlying member method code with example usage: obj.build(key) and returns: self