docs: def pairs(a):
      """Return array of pairs of adjacent elements in a.
  
      >>> pairs([1, 2, 3, 4])
      array([[1, 2],
             [2, 3],
             [3, 4]])
  
      """
      a = np.asarray(a)
      return as_strided(a, shape=(a.size - 1, 2), strides=a.strides * 2)