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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 find_rule(self, rule):
 """Find a Rule by name."""

        defrule = lib.EnvFindDefrule(self._env, rule.encode())
        if defrule == ffi.NULL:
            raise LookupError("Rule '%s' not found" % defrule)

        return Rule(self._env, defrule)