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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_node(self, child):
 """append a child, linking it in the tree"""

        # pylint: disable=no-member; depending by the class
        # which uses the current class as a mixin or base class.
        # It's rewritten in 2.0, so it makes no sense for now
        # to spend development time on it.
        self.body.append(child)
        child.parent = self