code: def make_dataset(N, train_length):
      # generates 2 ** N - 1 timeseries with constant increasing values
      n = 2**N - 1
  
      targets = np.arange(n * train_length).reshape((n, train_length))
  
      return ListDataset(
          [
              {"start": "2012-01-01", "target": targets[i, :]}
              for i in range(n)
          ],
          freq="D",
      )
  
file_path: gluonts/test/mx/model/seq2seq/test_forking_sequence_splitter.py
imports: import numpy
  import pytest
  from gluonts import transform
  from gluonts.dataset.common import ListDataset
  from gluonts.dataset.field_names import FieldName
  from gluonts.mx.model.seq2seq._transform import ForkingSequenceSplitter
  from gluonts.time_feature import time_features_from_frequency_str
  from gluonts.transform import TestSplitSampler
  from gluonts.transform import ValidationSplitSampler
label_desc: Use image node_id 1 for calling a global function with example usage: make_dataset(N, train_length) and returns: ListDataset