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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 _block_width(self):
 """ Return a |Length| object specifying the width of available "writing" space between the margins of the last section of this document. """

        section = self.sections[-1]
        return Emu(
            section.page_width - section.left_margin - section.right_margin
        )