Add a prefix.

def add(self):
        """ Add a prefix.
        """

        # pass prefix to template - if we have any
        if 'prefix' in request.params:
            c.prefix = request.params['prefix']
        else:
            c.prefix = ''

        c.search_opt_parent = "all"
        c.search_opt_child = "none"

        return render('/prefix_add.html')