class_docstr: Merge the ensemble_dict into an ensemble object.
  
  For example: {Rollinga_b: object, Rollingb_c: object} -> object
  
  When calling this class:
  
      Args:
          ensemble_dict (dict): the ensemble dict like {name: things} waiting for merging
  
      Returns:
          object: the ensemble object
class_docstr_tok: ["Merge","the","ensemble_dict","into","an","ensemble","object",".","For","example",":","{","Rollinga_b",":","object",",","Rollingb_c",":","object","}","-",">","object","When","calling","this","class",":","Args",":","ensemble_dict","(","dict",")",":","the","ensemble","dict","like","{","name",":","things","}","waiting","for","merging","Returns",":","object",":","the","ensemble","object"]
code: def __call__(self, ensemble_dict: dict, *args, **kwargs):
      raise NotImplementedError(
          f"Please implement the `__call__` method."
      )
  
file_path: qlib/qlib/model/ens/ensemble.py
imports: from typing import Union
  import pandas
  from qlib.utils import FLATTEN_TUPLE, flatten_dict
  from qlib.log import get_module_logger
label_desc: Use image node_id 1 for calling the Ensemble obj's underlying member method code with example usage: obj.__call__(ensemble_dict) without return types