code: def pset(iterable=(), pre_size=8):
      
      if not iterable:
          return _EMPTY_PSET
  
      return PSet._from_iterable(iterable, pre_size=pre_size)
docs: Creates a persistent set from iterable. Optionally takes a sizing parameter equivalent to that
      used for :py:func:`pmap`.
  
      >>> s1 = pset([1, 2, 3, 2])
      >>> s1
      pset([1, 2, 3])