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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 pretty_print(self, indent=0):
 """Print the document without tags using indentation """


        s = tab = ' '*indent
        s += '%s: ' %self.tag
        if isinstance(self.value, basestring):
            s += self.value
        else:
            s += '\n'
            for e in self.value:
                s += e.pretty_print(indent+4)
        s += '\n'

        return s