There are numerous typos in the docs. I should have been keeping a more careful list. This one is an actual function signature that was never updated, looks like.
http://www.clawpack.org/pyclaw/io.html has read_<format> and write_<format>, but the actual way things are read and written is via clawpack.pyclaw.fileio.<format>.read and clawpack.pyclaw.fileio.<format>.write. grep is giving me nothing for read_ascii, for example.