code: def invert(self):
          
          tmp = self["quote"]
          self["quote"] = self["base"]
          self["base"] = tmp
          if "for_sale" in self and self["for_sale"]:
              self["for_sale"] = self.amount_class(
                  self["for_sale"]["amount"] * self["price"], self["base"]["symbol"]
              )
          return self
docs: Invert the price (e.g. go from ``USD/BTS`` into ``BTS/USD``)