class_docstr: A Munch that calls a user-specified function to generate values for
  missing keys like collections.defaultdict.
  
  >>> b = DefaultFactoryMunch(list, {'hello': 'world!'})
  >>> b.hello
  'world!'
  >>> b.foo
  []
  >>> b.bar.append('hello')
  >>> b.bar
  ['hello']
code: def __missing__(self, k):
      self[k] = self.default_factory()
      return self[k]
  
imports: from collections.abc import Mapping
label_desc: Use image node_id 6 for calling the DefaultFactoryMunch obj's underlying member method code with example usage: obj.__missing__(k) and returns: self