code: def as_series(x):
      
      if isinstance(x, pd.Series):
          return x
      return pd.Series(column_or_1d(x))
docs: Cast as pandas Series.
  
      Cast an iterable to a Pandas Series object. Note that the index
      will simply be a positional ``arange`` and cannot be set in this
      function.
  
      Parameters
      ----------
      x : array-like, shape=(n_samples,)
          The 1d array on which to compute the auto correlation.
  
      Examples
      --------
      >>> as_series([1, 2, 3])
      0    1
      1    2
      2    3
      dtype: int64
  
      >>> as_series(as_series((1, 2, 3)))
      0    1
      1    2
      2    3
      dtype: int64
  
      >>> import pandas as pd
      >>> as_series(pd.Series([4, 5, 6], index=['a', 'b', 'c']))
      a    4
      b    5
      c    6
      dtype: int64
  
      Returns
      -------
      s : pd.Series
          A pandas Series object.