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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 gather_facts(self):
 """ Return the number of facts. """

        facts = []

        for file in self.yaml_files:
            facts += self.gather_facts_list(file)

        unique_facts = list(set(facts))
        self.facts = unique_facts

        return len(unique_facts)