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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 markers_pass(self, req, extras=None):
 """ Evaluate markers for req against each extra that demanded it. Return False if the req has a marker and fails evaluation. Otherwise, return True. """

        extra_evals = (
            req.marker.evaluate({'extra': extra})
            for extra in self.get(req, ()) + (extras or (None,))
        )
        return not req.marker or any(extra_evals)