code: def column_or_1d(y, warn=False):
      
      shape = np.shape(y)
      if len(shape) == 1:
          return np.ravel(y)
      if len(shape) == 2 and shape[1] == 1:
          if warn:
              warnings.warn("A column-vector y was passed when a 1d array was"
                            " expected. Please change the shape of y to "
                            "(n_samples, ), for example using ravel().",
                            DataConversionWarning, stacklevel=2)
          return np.ravel(y)
  
      raise ValueError("bad input shape {0}".format(shape))
docs: Ravel column or 1d numpy array, else raises an error
  
      Parameters
      ----------
      y : array-like
  
      Returns
      -------
      y : array