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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 append( self, moment_or_operation_tree: Union[ops.Moment, ops.OP_TREE], strategy: InsertStrategy = InsertStrategy.EARLIEST):
 """Appends operations onto the end of the circuit. Moments within the operation tree are appended intact. Args: moment_or_operation_tree: The moment or operation tree to append. strategy: How to pick/create the moment to put operations into. """

        self.insert(len(self._moments), moment_or_operation_tree, strategy)