code: def load_airline():
      """Load the airline univariate time series dataset [1].
  
      Returns
      -------
      y : pd.Series
          Time series
  
      Examples
      --------
      >>> from sktime.datasets import load_airline
      >>> y = load_airline()
  
      Notes
      -----
      The classic Box & Jenkins airline data. Monthly totals of international
      airline passengers, 1949 to 1960.
  
      Dimensionality:     univariate
      Series length:      144
      Frequency:          Monthly
      Number of cases:    1
  
      This data shows an increasing trend, non-constant (increasing) variance
      and periodic, seasonal patterns.
  
      References
      ----------
      .. [1] Box, G. E. P., Jenkins, G. M. and Reinsel, G. C. (1976) Time Series
            Analysis, Forecasting and Control. Third Edition. Holden-Day.
            Series G.
      """
      name = "Airline"
      fname = name + ".csv"
      path = os.path.join(MODULE, DIRNAME, name, fname)
      y = pd.read_csv(path, index_col=0, dtype={1: float}).squeeze(
          "columns"
      )
  
      # make sure time index is properly formatted
      y.index = pd.PeriodIndex(y.index, freq="M", name="Period")
      y.name = "Number of airline passengers"
      return y
  
imports: import os
  import zipfile
  from urllib.error import HTTPError, URLError
  from warnings import warn
  import numpy
  import pandas
  from sktime.datasets._data_io import _download_and_extract, _list_available_datasets, _load_dataset, _load_provided_dataset
  from sktime.datasets._readers_writers.tsf import load_tsf_to_dataframe
  from sktime.datasets.tsf_dataset_names import tsf_all, tsf_all_datasets
  from sktime.utils.validation._dependencies import _check_soft_dependencies
label_desc: Use image node_id 15 for calling a global function with example usage: load_airline() and returns: y