code: def _historical_forecasts_start_warnings(
      idx: int,
      start: Union[pd.Timestamp, int],
      start_time_: Union[int, pd.Timestamp],
      historical_forecasts_time_index: TimeIndex,
  ):
      """Warnings when start value provided by user is not within the forecastable indexes boundaries"""
      if not isinstance(start, pd.Timestamp):
          start_value_msg = f"value `{start}` corresponding to timestamp `{start_time_}`"
      else:
          start_value_msg = f"time `{start_time_}`"
  
      if start_time_ < historical_forecasts_time_index[0]:
          logger.warning(
              f"`start` {start_value_msg} is before the first predictable/trainable historical "
              f"forecasting point for series at index: {idx}. Ignoring `start` for this series and "
              f"beginning at first trainable/predictable time: {historical_forecasts_time_index[0]}. "
              f"To hide these warnings, set `show_warnings=False`."
          )
      else:
          logger.warning(
              f"`start` {start_value_msg} is after the last trainable/predictable historical "
              f"forecasting point for series at index: {idx}. This would results in empty historical "
              f"forecasts. Ignoring `start` for this series and beginning at first trainable/"
              f"predictable time: {historical_forecasts_time_index[0]}. Non-empty forecasts can be "
              f"generated by setting `start` value to times between (including): "
              f"{historical_forecasts_time_index[0], historical_forecasts_time_index[-1]}. "
              f"To hide these warnings, set `show_warnings=False`."
          )
  
imports: from types import SimpleNamespace
  from typing import Any, Callable, Dict, Optional, Sequence, Set, Tuple, Union
  import inspect
  import numpy
  import pandas
  from numpy.typing import ArrayLike
  from darts.logging import get_logger, raise_if_not, raise_log
  from darts.timeseries import TimeSeries
  from darts.utils.timeseries_generation import generate_index
  from darts.utils.utils import series2seq
label_desc: Use image node_id 4 for calling a global function with example usage: _historical_forecasts_start_warnings(idx, start, start_time_, historical_forecasts_time_index) without return types