class_docstr: A stack of dictionaries that behaves as a view on those dictionaries,
  giving preference to the last.
  
  >>> stack = DictStack([dict(a=1, c=2), dict(b=2, a=2)])
  >>> stack['a']
  2
  >>> stack['b']
  2
  >>> stack['c']
  2
  >>> len(stack)
  3
  >>> stack.push(dict(a=3))
  >>> stack['a']
  3
  >>> set(stack.keys()) == set(['a', 'b', 'c'])
  True
  >>> set(stack.items()) == set([('a', 3), ('b', 2), ('c', 2)])
  True
  >>> dict(**stack) == dict(stack) == dict(a=3, c=2, b=2)
  True
  >>> d = stack.pop()
  >>> stack['a']
  2
  >>> d = stack.pop()
  >>> stack['a']
  1
  >>> stack.get('b', None)
  >>> 'c' in stack
  True
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code: def __contains__(self, other):
      return collections.abc.Mapping.__contains__(self, other)
  
file_path: catboost/contrib/python/setuptools/py3/setuptools/_distutils/_collections.py
imports: import collections
  import functools
  import itertools
  import operator
label_desc: Use image node_id 3 for calling the DictStack obj's underlying member method code with example usage: obj.__contains__(other) and returns: collections