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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def AddWatchOnly(self, script_hash):
 """ 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. """

        if script_hash in self._contracts:
            logger.error("Address already in contracts")
            return

        self._watch_only.append(script_hash)