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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 blob_size(self, digest):
 """ Return the size of a blob in the registry given the hash of its content. :param digest: Hash of the blob's content (prefixed by ``sha256:``). :type digest: str :rtype: long :returns: Whether the blob exists. """

        r = self._request('head', 'blobs/' + digest)
        return long(r.headers['content-length'])