What am I missing?

[jdevng]

I am using the example on the main page - is there a context to the underscore?

import msgpack
msgpack.packb([1, 2, 3], use_bin_type=True)
msgpack.unpack(_, raw=False)
exit()

Results in error:

msgpack.unpackb(_, raw=False)
NameError: name '_' is not defined

I am trying to serialize to all binary/hex.