code: def _const_fill(series: TimeSeries, fill: float = 0) -> TimeSeries:
      """
      Fills the missing values of `series` with only the value provided (default zeroes).
  
      Parameters
      ----------
      series
          The TimeSeries to check for missing values.
      fill
          The value used to replace the missing values.
  
      Returns
      -------
      TimeSeries
          A TimeSeries, `series` with all missing values set to `fill`.
      """
  
      return TimeSeries.from_times_and_values(
          series.time_index,
          series.pd_dataframe().fillna(value=fill),
          freq=series.freq,
          columns=series.columns,
          static_covariates=series.static_covariates,
          hierarchy=series.hierarchy,
      )
  
imports: from typing import List, Optional, Union
  from darts.logging import get_logger, raise_if, raise_if_not
  from darts.timeseries import TimeSeries
label_desc: Use image node_id 4 for calling a global function with example usage: _const_fill(series, fill) and returns: TimeSeries