code: def transform(self, series: np.array) -> pd.Series:
      series = self._flatten_series(series)
      return self.diff(series).shift(1).fillna(0)
  
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 4 for calling the Differencer obj's underlying member method code with example usage: obj.transform(series) and returns: self