it is interesting to see that the code associate the term cold to a negative sentiment while for warm it provides a postive sentiment. In the reviews try this:
‘The mochi is cold’
then try
‘The mochi is warm’
As you all know mochi si naturally cold not warm, then why the sentiment is negative?
I would guess the language model doesn’t know what “mochi” is. Or the relationship between mochi and its temperature were not included in the training set.
There are several non-universal assumptions in that statement.
Still, @Daniele_B, have you tried mochi ice-cream? 
this would be an interesting followup project for fine-tuning, to see if we can fine-tune the model to understand this new relationship.