class_docstr: A persistent bag/multiset type.
  
  Requires elements to be hashable, and allows duplicates, but has no
  ordering. Bags are hashable.
  
  Do not instantiate directly, instead use the factory functions :py:func:`b`
  or :py:func:`pbag` to create an instance.
  
  Some examples:
  
  >>> s = pbag([1, 2, 3, 1])
  >>> s2 = s.add(4)
  >>> s3 = s2.remove(1)
  >>> s
  pbag([1, 1, 2, 3])
  >>> s2
  pbag([1, 1, 2, 3, 4])
  >>> s3
  pbag([1, 2, 3, 4])
docstr: Check if an element is in the bag.
  
  >>> 1 in pbag([1, 1, 2])
  True
  >>> 0 in pbag([1, 2])
  False
docstr_tok: ["Check","if","an","element","is","in","the","bag",".",">",">",">","1","in","pbag","(","[","1",",","1",",","2","]",")","True",">",">",">","0","in","pbag","(","[","1",",","2","]",")","False"]
code: def __contains__(self, elt):
      """
      Check if an element is in the bag.
  
      >>> 1 in pbag([1, 1, 2])
      True
      >>> 0 in pbag([1, 2])
      False
      """
      return elt in self._counts
  
imports: from collections.abc import Container, Iterable, Sized, Hashable
  from functools import reduce
  from typing import Generic, TypeVar
  from pyrsistent._pmap import pmap
label_desc: Use image node_id 8 for calling the PBag obj's underlying member method code with example usage: obj.__contains__(elt) and returns: unknown