def new(arg_name, annotated_with=None):
    """Creates a BindingKey.

    Args:
      arg_name: the name of the bound arg
      annotation: an Annotation, or None to create an unannotated binding key
    Returns:
      a new BindingKey
    """
    if annotated_with is not None:
        annotation = annotations.Annotation(annotated_with)
    else:
        annotation = annotations.NO_ANNOTATION
    return BindingKey(arg_name, annotation)
Creates a BindingKey.

    Args:
      arg_name: the name of the bound arg
      annotation: an Annotation, or None to create an unannotated binding key
    Returns:
      a new BindingKey