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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 spec(self):
 """Return a SourceSpec to describe this source"""

        from ambry_sources.sources import SourceSpec

        d = self.dict
        d['url'] = self.url

        # Will get the URL twice; once as ref and once as URL, but the ref is ignored

        return SourceSpec(**d)