The functions \cs_get_arg_count_from_signature:N and
\cs_split_function:NN have been move to 'internal' status, and so may be
renamed or dropped in the future without notice. These functions are not
used outside of the kernel in a current TeX Live installation.
The functions \cs_get_function_name:NN and \cs_get_function_signature:NN
are deprecated, and will be removed from expl3 by 2012-08-31. These
functions are entirely unused in a current TeX Live installation.