class_docstr: Util mixin indicator class
docstr: Check if fillna flag is True.
  
  Args:
      series(pandas.Series): calculated indicator series.
      value(int): value to fill gaps; if -1 fill values using 'backfill' mode.
  
  Returns:
      pandas.Series: New feature generated.
code: def _check_fillna(
      self, series: pd.Series, value: int = 0
  ) -> pd.Series:
      """Check if fillna flag is True.
  
      Args:
          series(pandas.Series): calculated indicator series.
          value(int): value to fill gaps; if -1 fill values using 'backfill' mode.
  
      Returns:
          pandas.Series: New feature generated.
      """
      if self._fillna:
          series_output = series.copy(deep=False)
          series_output = series_output.replace(
              [np.inf, -np.inf], np.nan
          )
          if isinstance(value, int) and value == -1:
              series = series_output.ffill().bfill()
          else:
              series = series_output.ffill().fillna(value)
      return series
  
file_path: ta/ta/utils.py
imports: import math
  import numpy
  import pandas
label_desc: Use image node_id 1 for calling the IndicatorMixin obj's underlying member method code with example usage: obj._check_fillna(series, value) and returns: series