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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 iter_edges(self, cached_content=None):
 """ Iterate over the list of edges of a tree. Each egde is represented as a tuple of two elements, each containing the list of nodes separated by the edge. """

        if not cached_content:
            cached_content = self.get_cached_content()
        all_leaves = cached_content[self]
        for n, side1 in six.iteritems(cached_content):
            yield (side1, all_leaves - side1)