def _include_file(context, uri, calling_uri, **kwargs):
    """locate the template from the given uri and include it in
    the current output."""

    template = _lookup_template(context, uri, calling_uri)
    (callable_, ctx) = _populate_self_namespace(
                                context._clean_inheritance_tokens(),
                                template)
    callable_(ctx, **_kwargs_for_include(callable_, context._data, **kwargs))
locate the template from the given uri and include it in
    the current output.