code: def column_or_1d(y, warn=False):
      """Ravel column or 1d numpy array, else raises an error
  
      Parameters
      ----------
      y : array-like
  
      warn : boolean, default False
         To control display of warnings.
  
      Returns
      -------
      y : array
  
      """
      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))
  
imports: import warnings
  import numbers
  import numpy
  import scipy.sparse
  from ..externals import six
  from ..utils.fixes import signature
  from .deprecation import deprecated
  from ..exceptions import DataConversionWarning
  from ..exceptions import NonBLASDotWarning
  from ..exceptions import NotFittedError
label_desc: Use image node_id 12 for calling a global function with example usage: column_or_1d(y, warn) and returns: np, np