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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, node):
 """To append a new child."""

        if node.parent == self.key and not self.elapsed_time:
            self.children.append(node)
        else:
            # Recursive call
            for child in self.children:
                if not child.elapsed_time:
                    child.append(node)