'Returns a list of dict describing fixed buttons used for filtering.
Each list item should be a dict with the following keys:
* ``text``: Text to display on the button
* ``icon``: Icon class for icon element (inserted before text).
* ``value``: Value returned when the button is clicked. This value is
passed to ``filter()`` as ``filter_string``.'

def get_fixed_buttons(self):

    return []
