def METHOD_NAME(self) -> None:
    """
    Unregister the base module in ``sys.modules``.
    Keep everything except the modules name (allowing re-registration).
    """
    # Cleanup `sys.modules`.
    sys.modules.pop(self._module_name, None)
    for submodule_name in self._submodules.keys():
        sys.modules.pop("{:s}.{:s}".format(self._module_name, submodule_name), None)
    # Remove from self.
    self._submodules.clear()
    self._module = None