class_docstr: Force Index (FI)
  
  It illustrates how strong the actual buying or selling pressure is. High
  positive values mean there is a strong rising trend, and low values signify
  a strong downward trend.
  
  http://stockcharts.com/school/doku.php?id=chart_school:technical_indicators:force_index
  
  Args:
      close(pandas.Series): dataset 'Close' column.
      volume(pandas.Series): dataset 'Volume' column.
      window(int): n period.
      fillna(bool): if True, fill nan values.
code: def __init__(
      self,
      close: pd.Series,
      volume: pd.Series,
      window: int = 13,
      fillna: bool = False,
  ):
      self._close = close
      self._volume = volume
      self._window = window
      self._fillna = fillna
      self._run()
  
imports: import typing
  import numpy
  import pandas
  from ta.utils import IndicatorMixin, _ema
label_desc: Use image node_id 1 to create a new ForceIndexIndicator object from inherited base classes: IndicatorMixin with example: obj = ForceIndexIndicator(close, volume, window, fillna)