class_docstr: Cache for Or operation between filters. 
code: def __missing__(self, filters):
      a, b = filters
      assert isinstance(b, Filter), "Expecting filter, got %r" % b
  
      if isinstance(b, Always) or isinstance(a, Never):
          return b
      elif isinstance(b, Never) or isinstance(a, Always):
          return a
  
      result = _OrList(filters)
      self[filters] = result
      return result
  
imports: from __future__ import unicode_literals
  from abc import ABCMeta, abstractmethod
  from six import with_metaclass
  from prompt_toolkit.utils import test_callable_args
label_desc: Use image node_id 1 for calling the _OrCache obj's underlying member method code with example usage: obj.__missing__(filters) and returns: result, b, a