code: def __call__(self, index: pd.DatetimeIndex) -> np.ndarray:
      values = getattr(index, self.freq)
      num_values = max(values) + 1
      steps = [x * 2.0 * np.pi / num_values for x in values]
      return np.vstack([np.cos(steps), np.sin(steps)])
  
file_path: gluonts/src/gluonts/nursery/robust-mts-attack/pts/feature/fourier_date_feature.py
imports: from typing import List
  import numpy
  import pandas
  from pandas.tseries.frequencies import to_offset
  from gluonts.core.component import validated
  from gluonts.time_feature import TimeFeature, norm_freq_str
label_desc: Use image node_id 2 for calling the FourierDateFeatures obj's underlying member method code with example usage: obj.__call__(index) and returns: np