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If ARG is a positive number, Gnus will use that as the startup
level. If ARG is nil, Gnus will be started at level 2. If ARG is
non-nil and not a positive number, Gnus will prompt the user for the
name of an NNTP server to use.
As opposed to `gnus', this command will not connect to the local
(fn &optional ARG SLAVE)