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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 PrintTree(self, depth=''):
 """Print the tree."""

    result = '{0:s}{1:s}\n'.format(depth, self.operator)
    for part in self.args:
      result += '{0:s}-{1:s}\n'.format(depth, part.PrintTree(depth + '  '))

    return result