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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 facts(self):
 """Iterate over the asserted Facts."""

        fact = lib.EnvGetNextFact(self._env, ffi.NULL)

        while fact != ffi.NULL:
            yield new_fact(self._env, fact)

            fact = lib.EnvGetNextFact(self._env, fact)