like search_features
, but instead of return hits only adds a column to the token data that contains a code (the query label) for tokens that match the query.
Note that only one code can be assigned to each token, so if there are overlapping results for different queries, the code for the last query
will be used. This means that the order of queries (in the query argument) matters.
Usage:
## R6 method for class tCorpus. Use as tc$method (where tc is a tCorpus object).
code_features(query, code=NULL, feature='token', column='code', ...)