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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 pop(self, identifier, default=None):
 """Pop a node of the AttrTree using its path string. Args: identifier: Path string of the node to return default: Value to return if no node is found Returns: The node that was removed from the AttrTree """

        if identifier in self.children:
            item = self[identifier]
            self.__delitem__(identifier)
            return item
        else:
            return default