code: def AddWatchOnly(self, script_hash):
          
          if script_hash in self._contracts:
              logger.error("Address already in contracts")
              return
  
          self._watch_only.append(script_hash)
docs: Add a watch only address to the wallet.
  
          Args:
              script_hash (UInt160): a bytearray (len 20) representing the public key.
  
          Note:
              Prints a warning to the console if the address already exists in the wallet.