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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 as_bel(self) -> str: """Return this fusion as a BEL string."""

        return '{}(fus({}:{}, "{}", {}:{}, "{}"))'.format(
            self._func,
            self.partner_5p.namespace,
            self.partner_5p._priority_id,
            self.range_5p.as_bel(),
            self.partner_3p.namespace,
            self.partner_3p._priority_id,
            self.range_3p.as_bel(),
        )