code: def union1d(ar1, ar2):
      """
      Find the union of two arrays.
  
      Return the unique, sorted array of values that are in either of the two
      input arrays.
  
      Parameters
      ----------
      ar1, ar2 : array_like
          Input arrays. They are flattened if they are not already 1D.
  
      Returns
      -------
      union1d : ndarray
          Unique, sorted union of the input arrays.
  
      Examples
      --------
      >>> np.union1d([-1, 0, 1], [-2, 0, 2])
      array([-2, -1,  0,  1,  2])
  
      To find the union of more than two arrays, use functools.reduce:
  
      >>> from functools import reduce
      >>> reduce(np.union1d, ([1, 3, 4, 3], [3, 1, 2, 1], [6, 3, 4, 2]))
      array([1, 2, 3, 4, 6])
      """
      return unique(np.concatenate((ar1, ar2), axis=None))
  
imports: import functools
  import warnings
  from typing import NamedTuple
  import numpy
  from numpy._core import overrides
label_desc: Use image node_id 25 for calling a global function with example usage: union1d(ar1, ar2) and returns: unique