class_docstr: Persistent set implementation. Built on top of the persistent map. The set supports all operations
  in the Set protocol and is Hashable.
  
  Do not instantiate directly, instead use the factory functions :py:func:`s` or :py:func:`pset`
  to create an instance.
  
  Random access and insert is log32(n) where n is the size of the set.
  
  Some examples:
  
  >>> s = pset([1, 2, 3, 1])
  >>> s2 = s.add(4)
  >>> s3 = s2.remove(2)
  >>> s
  pset([1, 2, 3])
  >>> s2
  pset([1, 2, 3, 4])
  >>> s3
  pset([1, 3, 4])
code: def __repr__(self):
      if PY2 or not self:
          return "p" + str(set(self))
  
      return "pset([{0}])".format(str(set(self))[1:-1])
  
imports: from ._compat import Set, Hashable
  import sys
  from pyrsistent._pmap import pmap
label_desc: Use image node_id 5 for calling the PSet obj's underlying member method code with example usage: obj.__repr__() and returns: str, unknown