code: def nans(length):
      """Return a vector of NaNs, of length `length`."""
      return np.full(length, np.nan)
  
file_path: sktime/sktime/forecasting/base/adapters/_tbats.py
imports: import numpy
  import pandas
  from sktime.forecasting.base import BaseForecaster
  from sktime.utils.validation import check_n_jobs
  from sktime.utils.validation.forecasting import check_sp
label_desc: Use image node_id 1 for calling a global function with example usage: nans(length) and returns: np