def save_model(self, model, meta_data=None, index_fields=None):
return self.adapter.save_model(model, meta_data, index_fields)<EOL>
saves the model instance to riak

Args:
    meta (dict): JSON serializable meta data for logging of save operation.
        {'lorem': 'ipsum', 'dolar': 5}
    index_fields (list): Tuple list for secondary indexing keys in riak (with 'bin' or 'int').
        [('lorem','bin'),('dolar','int')]
:return: