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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def save_model(self, model, meta_data=None, index_fields=None):
 """ 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: """

        return self.adapter.save_model(model, meta_data, index_fields)