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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 _get_tree(self, code, lines, marker, indent):
 """Build a tree to illustrate the way the Wikicode object was parsed. The method that builds the actual tree is ``__showtree__`` of ``Node`` objects. *code* is the ``Wikicode`` object to build a tree for. *lines* is the list to append the tree to, which is returned at the end of the method. *marker* is some object to be used to indicate that the builder should continue on from the last line instead of starting a new one; it should be any object that can be tested for with ``is``. *indent* is the starting indentation. """

        def write(*args):
            """Write a new line following the proper indentation rules."""
            if lines and lines[-1] is marker:  # Continue from the last line
                lines.pop()  # Remove the marker
                last = lines.pop()
                lines.append(last + " ".join(args))
            else:
                lines.append(" " * 6 * indent + " ".join(args))

        get = lambda code: self._get_tree(code, lines, marker, indent + 1)
        mark = lambda: lines.append(marker)
        for node in code.nodes:
            node.__showtree__(write, get, mark)
        return lines