code: def without(seq1, seq2):
      r
      if isSet(seq2): d2 = seq2
      else: d2 = set(seq2)
      return [elt for elt in seq1 if elt not in d2]
docs: r"""Return a list with all elements in `seq2` removed from `seq1`, order
      preserved.
  
      Examples:
  
      >>> without([1,2,3,1,2], [1])
      [2, 3, 2]