The module docstring, and all function, class and method docstrings are

searched. Objects imported into the module are not searched.

..currentmodule::None

..attribute::module.__test__

..currentmodule::doctest

In addition, there are cases when you want tests to be part of a module but not part

of the help text, which requires that the tests not be included in the docstring.

Doctest looks for a module-level variable called ``__test__`` and uses it to locate other