class_docstr: An object which handles communicating with metadata db through MLMD.
code: def get_best_k(self, trials=None, k=1, valid_only=False):
      return None
  
file_path: model_search/model_search/metadata/mock_metadata.py
imports: from model_search.metadata import metadata
label_desc: Use image node_id 6 for calling the MockMetaData obj's underlying member method code with example usage: obj.get_best_k(trials, k, valid_only) and returns: None