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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 add_child(self, child):
        '''Add child to ``Node`` object

        Args:
            ``child`` (``Node``): The child ``Node`` to be added
        '''
        if not isinstance(child, Node):
            raise TypeError("child must be a Node")
        self.children.append(child); child.parent = self