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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 latex_repr(self):
 """A LaTeX representation for the unit Examples -------- '\\\\frac{\\\\rm{g}}{\\\\rm{cm}^{3}}' """

        if self._latex_repr is not None:
            return self._latex_repr
        if self.expr.is_Atom:
            expr = self.expr
        else:
            expr = self.expr.copy()
        self._latex_repr = _get_latex_representation(expr, self.registry)
        return self._latex_repr