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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 chromsizes(self, uid):
 """ Return the chromosome sizes from the given filename """

        url = "http://{host}:{port}/api/v1/chrom-sizes/?id={uid}".format(
            host=self.host, port=self.port, uid=uid
        )

        req = requests.get(url)
        if req.status_code != 200:
            raise ServerError("Error fetching chromsizes:", req.content)

        return req.content