code: def load_key(self, key):
      return self._preloaded.get(key)
  
file_path: metaflow/metaflow/datastore/datastore_set.py
imports: import json
  from io import BytesIO
  from .exceptions import DataException
  from .content_addressed_store import BlobCache
label_desc: Use image node_id 2 for calling the ImmutableBlobCache obj's underlying member method code with example usage: obj.load_key(key) and returns: self