code: def flat_params():
      return (
          [f"x[{i}]" for i in range(3)]
          + [f"y[{i},{j}]" for i in range(2) for j in range(3)]
          + ["z"]
      )
  
imports: import numpy
  import pandas
  import pytest
  from sklearn.ensemble import AdaBoostRegressor, BaggingRegressor, ExtraTreesRegressor, GradientBoostingRegressor, RandomForestRegressor
  from orion.analysis.base import average, flatten_numpy, flatten_params, ranking, to_numpy, train_regressor
  from orion.core.io.space_builder import SpaceBuilder
  from orion.core.worker.transformer import build_required_space
label_desc: Use image node_id 5 for calling a global function with example usage: flat_params() and returns: unknown