e interpreter)

    Usage: construct a docstring.Substitution with a sequence or
    dictionary suitable for performing substitution; then
    decorate a suitable function with the constructed object. e.g.

    sub_author_name = Substitution(author='Jason')

    @sub_author_name
    def some_function(x):
        "%(author)s wrote this function"

    # note that some_function.__doc__ is now "Jason wrote this function"

    One can also use positional arguments.

    sub_first_last_names = Substitution('Edgar Allen', 'Poe')

    @sub_first_last_names
    def some_function(x):
        "%s %s wrote the Raven"
    r