docs: def unique(ar):
      r"""Find the unique elements of an array.
  
      It uses ``dask.array.unique`` if necessary.
  
      Args:
          ar (array_like): Input array.
  
      Returns:
          array_like: the sorted unique elements.
      """
  
      import dask.array as da
  
      if isinstance(ar, da.core.Array):
          return da.unique(ar)
  
      return _unique(ar)