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