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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 to_string(self, indent="", newl="", addindent=""):
        '''
        Returns a string representation of the XMLi element.
        @return: str
        '''
        buf = StringIO()
        self.to_xml().writexml(buf, indent=indent, addindent=addindent,
                               newl=newl)
        return buf.getvalue()