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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 load_signature(stream, original_data):
 """Load signature from stream, and compute GPG digest for verification."""

    signature, = list(parse_packets((stream)))
    hash_alg = HASH_ALGORITHMS[signature['hash_alg']]
    digest = digest_packets([{'_to_hash': original_data}, signature],
                            hasher=hashlib.new(hash_alg))
    assert signature['hash_prefix'] == digest[:2]
    return signature, digest