code: def append_create_passive_offer_op(self,
                                         selling_code,
                                         selling_issuer,
                                         buying_code,
                                         buying_issuer,
                                         amount,
                                         price,
                                         source=None):
          
          selling = Asset(selling_code, selling_issuer)
          buying = Asset(buying_code, buying_issuer)
          op = operation.CreatePassiveOffer(selling, buying, amount, price,
                                            source)
          return self.append_op(op)
docs: Append a :class:`CreatePassiveOffer
          <stellar_base.operation.CreatePassiveOffer>` operation to the list of
          operations.
  
          :param str selling_code: The asset code for the asset the offer creator
              is selling.
          :param selling_issuer: The issuing address for the asset the offer
              creator is selling.
          :type selling_issuer: str, None
          :param str buying_code: The asset code for the asset the offer creator
              is buying.
          :param buying_issuer: The issuing address for the asset the offer
              creator is selling.
          :type buying_issuer: str, None
          :param str amount: Amount of the asset being sold. Set to 0 if you want
              to delete an existing offer.
          :param price: Price of 1 unit of selling in terms of buying. You can pass
              in a number as a string or a dict like `{n: numerator, d: denominator}`
          :type price: str, dict
          :param str source: The source address that is creating a passive offer
              on Stellar's distributed exchange.
          :return: This builder instance.