code: def register_pattern(name, pattern_factory, override=None):
  	
  	if not isinstance(name, string_types):
  		raise TypeError("name:{!r} is not a string.".format(name))
  	if not callable(pattern_factory):
  		raise TypeError("pattern_factory:{!r} is not callable.".format(pattern_factory))
  	if name in _registered_patterns and not override:
  		raise AlreadyRegisteredError(name, _registered_patterns[name])
  	_registered_patterns[name] = pattern_factory
docs: Registers the specified pattern factory.
  
  	*name* (:class:`str`) is the name to register the pattern factory
  	under.
  
  	*pattern_factory* (:class:`~collections.abc.Callable`) is used to
  	compile patterns. It must accept an uncompiled pattern (:class:`str`)
  	and return the compiled pattern (:class:`.Pattern`).
  
  	*override* (:class:`bool` or :data:`None`) optionally is whether to
  	allow overriding an already registered pattern under the same name
  	(:data:`True`), instead of raising an :exc:`AlreadyRegisteredError`
  	(:data:`False`). Default is :data:`None` for :data:`False`.