 models, represented by <code>sbo_kgram_freqs</code> and
<code>sbo_predtable</code> objects respectively, to objects of a smaller N-gram
order, N &lt; M. For k-gram frequency objects, frequency tables for
k &gt; N are simply dropped. For <code>sbo_predtable</code>'s, the predictions coming
from the nested N-gram model are instead retained. In both cases, all other
other attributes besides k-gram order (such as the corpus preprocessing
function, or the <code>lambda</code> penalty in Stupid Back-Off training)