code: def _testcase_series(
      freq: str, index_type: Callable, dtype=np.float32
  ):
      series = [
          pd.Series(
              np.arange(10, dtype=dtype),
              index_type("2021-01-01 00:00:00", periods=10, freq=freq),
          ),
          pd.Series(
              np.arange(20, dtype=dtype),
              index_type("2021-01-02 00:00:00", periods=20, freq=freq),
          ),
          pd.Series(
              np.arange(30, dtype=dtype),
              index_type("2021-01-03 00:00:00", periods=30, freq=freq),
          ),
      ]
  
      dataset = pandas.PandasDataset(series)
  
      expected_entries = [
          {
              "start": pd.Period(s.index[0], freq=freq),
              "target": s.values,
          }
          for s in series
      ]
  
      return dataset, expected_entries
  
imports: import io
  from typing import Callable, List, Union
  import pandas
  import numpy
  import pytest
  from gluonts.dataset import pandas
  from gluonts.testutil.equality import assert_recursively_equal
label_desc: Use image node_id 13 for calling a global function with example usage: _testcase_series(freq, index_type, dtype) and returns: dataset,  expected_entries