class_docstr: Configuration object
  
  Provides default values configurable at different levels. The configuration object can have
  global default values, which may be overridden by user with yaml configuration files,
  environment variables or by setting directly the values in the configuration object. In order,
  direct definition overrides, environment variables, which overrides yaml configuration, which
  overrides default values in configuration object definition.
  
  Examples
  --------
  >>> config = Configuration()
  >>> config.add_option('test', str, 'hello', 'TEST_ENV')
  >>> config.test
  'hello'
  >>> config.load_yaml('some_config.yaml')
  >>> config.test
  'in yaml!'
  >>> os.environ['TEST_ENV'] = 'there!'
  >>> config.test
  'there!'
  >>> config.test = 'here'
  >>> config.test
  'here'
class_docstr_tok: ["Configuration","object","Provides","default","values","configurable","at","different","levels",".","The","configuration","object","can","have","global","default","values",",","which","may","be","overridden","by","user","with","yaml","configuration","files",",","environment","variables","or","by","setting","directly","the","values","in","the","configuration","object",".","In","order",",","direct","definition","overrides",",","environment","variables",",","which","overrides","yaml","configuration",",","which","overrides","default","values","in","configuration","object","definition",".","Examples","--","--","--","--",">",">",">","config","=","Configuration","(",")",">",">",">","config.add_option","(","'test","'",",","str",",","'hello","'",",","'TEST_ENV","'",")",">",">",">","config.test","'hello'",">",">",">","config.load_yaml","(","'some_config.yaml","'",")",">",">",">","config.test","'in","yaml","!","'",">",">",">","os.environ","[","'TEST_ENV","'","]","=","'there","!","'",">",">",">","config.test","'there","!","'",">",">",">","config.test","=","'here'",">",">",">","config.test","'here","'"]
docstr: Return True if the option is defined.
docstr_tok: ["Return","True","if","the","option","is","defined","."]
code: def __contains__(self, key):
      """Return True if the option is defined."""
      return key in self._config or key in self._subconfigs
  
imports: import contextlib
  import logging
  import os
  import pprint
  import yaml
label_desc: Use image node_id 14 for calling the Configuration obj's underlying member method code with example usage: obj.__contains__(key) and returns: unknown