code: def FindUnspentCoinsByAsset(self, asset_id, from_addr=None, use_standard=False, watch_only_val=0):
          
          coins = self.FindUnspentCoins(from_addr=from_addr, use_standard=use_standard, watch_only_val=watch_only_val)
  
          return [coin for coin in coins if coin.Output.AssetId == asset_id]
docs: Finds unspent coin objects in the wallet limited to those of a certain asset type.
  
          Args:
              asset_id (UInt256): a bytearray (len 32) representing an asset on the blockchain.
              from_addr (UInt160): a bytearray (len 20) representing an address.
              use_standard (bool): whether or not to only include standard contracts ( i.e not a smart contract addr ).
              watch_only_val (int): a flag ( 0 or 64 ) indicating whether or not to find coins that are in 'watch only' addresses.
  
          Returns:
              list: a list of ``neo.Wallet.Coin`` in the wallet that are not spent