'Convert the applicable objects and assoc. data into a param dict
for a url query string to add to the url that loads the visualization.'

def get_url_params(self, trans, target_object, param_data):

    params = {}
    for (to_param_name, to_param_data) in param_data.items():
        target_attr = to_param_data.get('param_attr', None)
        assign = to_param_data.get('assign', None)
        if (target_attr and vis_utils.hasattr_recursive(target_object, target_attr)):
            params[to_param_name] = vis_utils.getattr_recursive(target_object, target_attr)
        if assign:
            params[to_param_name] = assign
    if params:
        params = trans.security.encode_dict_ids(params)
    return params
