code: def inverse_transform(
      self, series: pd.Series, init=None
  ) -> pd.Series:
      origin = init if init else self.last_train_value
      s = pd.Series(origin)
      s = s.append(series).dropna()
      return s.expanding().sum()
  
file_path: lightwood/lightwood/helpers/ts.py
imports: from typing import Tuple, Dict
  from datetime import datetime
  import numpy
  import pandas
label_desc: Use image node_id 5 for calling the Differencer obj's underlying member method code with example usage: obj.inverse_transform(series, init) and returns: s