code: def custom_tscv():
      # periods_between_splits is less than forecast_horizon
      # so there are
      return RollingTimeSeriesSplit(
          forecast_horizon=2 * 7,
          min_train_periods=10 * 7,
          expanding_window=True,
          use_most_recent_splits=True,
          periods_between_splits=1 * 7,
          periods_between_train_test=2 * 7,
          max_splits=3,
      )
  
imports: import pickle
  import sys
  import numpy
  import pandas
  import pytest
  from plotly.colors import DEFAULT_PLOTLY_COLORS
  from greykite.algo.forecast.silverkite.constants.silverkite_holiday import SilverkiteHoliday
  from greykite.common.constants import ACTUAL_COL
  from greykite.common.constants import PREDICTED_COL
  from greykite.common.constants import PREDICTED_LOWER_COL
  from greykite.common.constants import PREDICTED_UPPER_COL
  from greykite.common.constants import TIME_COL
  from greykite.common.constants import VALUE_COL
  from greykite.common.evaluation import EvaluationMetricEnum
  from greykite.common.evaluation import root_mean_squared_error
  from greykite.common.python_utils import assert_equal
  from greykite.common.testing_utils import generate_df_with_reg_for_tests
  from greykite.framework.benchmark.benchmark_class import BenchmarkForecastConfig
  from greykite.framework.constants import FORECAST_STEP_COL
  from greykite.framework.templates.autogen.forecast_config import ComputationParam
  from greykite.framework.templates.autogen.forecast_config import EvaluationMetricParam
  from greykite.framework.templates.autogen.forecast_config import EvaluationPeriodParam
  from greykite.framework.templates.autogen.forecast_config import ForecastConfig
  from greykite.framework.templates.autogen.forecast_config import MetadataParam
  from greykite.framework.templates.autogen.forecast_config import ModelComponentsParam
  from greykite.framework.templates.forecaster import Forecaster
  from greykite.framework.templates.model_templates import ModelTemplateEnum
  from greykite.sklearn.cross_validation import RollingTimeSeriesSplit
label_desc: Use image node_id 3 for calling a global function with example usage: custom_tscv() and returns: RollingTimeSeriesSplit