That's good point. I agree that the default value has to be ``None``. And I want to rename "context" to "options" for getting an uniformity with ``silk_options``. And same reason, ``silk_options`` should be a normal argument not a ``**kwargd``.

    def __init__(self, base, browse_root=None, add_url_rules=True,
                 template_options=None, silk_options=None):
        if template_options is None:
            template_options = {}
        if silk_options is None:
            silk_options = {}

How think of this?