code: def data_iterator(ts):
      """
      :param ts: list of pd.Series or pd.DataFrame
      :return:
      """
      for i in range(len(ts)):
          yield ts[i]
  
file_path: gluonts/test/evaluation/test_evaluator.py
imports: import numpy
  import pandas
  import pytest
  from gluonts.evaluation import Evaluator, MultivariateEvaluator, aggregate_valid
  from gluonts.model.forecast import QuantileForecast, SampleForecast
label_desc: Use image node_id 1 for calling a global function with example usage: data_iterator(ts) without return types