code: def get_historic_prices(self, **params):
          
          if 'currency_pair' in params:
              currency_pair = params['currency_pair']
          else:
              currency_pair = 'BTC-USD'
          response = self._get('v2', 'prices', currency_pair, 'historic', params=params)
          return self._make_api_object(response, APIObject)
docs: https://developers.coinbase.com/api/v2#get-historic-prices