def untrain(category, text)
      word_hash = Hasher.word_hash(text, @enable_stemmer,
                                   tokenizer: @tokenizer, token_filters: @token_filters)
      return if word_hash.empty?

      category = CategoryNamer.prepare_name(category)
      word_hash.each do |word, count|
        next if @backend.total_words < 0

        orig = @backend.category_word_frequency(category, word) || 0
        @backend.update_category_word_frequency(category, word, -count)
        if @backend.category_word_frequency(category, word) <= 0
          @backend.delete_category_word(category, word)
          count = orig
        end

        @backend.update_category_word_count(category, -count) if @backend.category_word_count(category) >= count
        @backend.update_total_words(-count)
      end
      @backend.update_total_trainings(-1)
      @backend.update_category_training_count(category, -1)
    end
def untrain(category, text)
      word_hash = Hasher.word_hash(text, @enable_stemmer,
                                   tokenizer: @tokenizer, token_filters: @token_filters)
      return if word_hash.empty?

      category = CategoryNamer.prepare_name(category)
      word_hash.each do |word, count|
        next if @backend.total_words < 0

        orig = @backend.category_word_frequency(category, word) || 0
        @backend.update_category_word_frequency(category, word, -count)
        if @backend.category_word_frequency(category, word) <= 0
          @backend.delete_category_word(category, word)
          count = orig
        end

        @backend.update_category_word_count(category, -count) if @backend.category_word_count(category) >= count
        @backend.update_total_words(-count)
      end
      @backend.update_total_trainings(-1)
      @backend.update_category_training_count(category, -1)
    end
Provides a untraining method for all categories specified in Bayes#new
 Be very careful with this method.

 For example:
     b = ClassifierReborn::Bayes.new 'This', 'That', 'the_other'
     b.train :this, "This text"
     b.untrain :this, "This text"