A struct entry that represents the counts of words in a text. This is an abstract type that should generally not be used as a column: instead, use [unigrams], [bigrams], [trigrams], etc.
At least two columns are required in the struct:
count. If the tokenization includes part-of-speech tags, they should be included as
count must be an integer.
word2, etc. should be either UTF-8 encoded strings or NULL. NULL values
indicate the removal of a token, to preserve privacy, copyright, etc.