You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: app.rb
    path of file: ./repos/picky/server/prototypes/facets
    
    the code of the file until where you have to start completion: require 'picky'

data 
    
  def facets category
    self[category].exact.inverted.inject({}) { |result, token_ids|
      token, ids = token_ids
      result[token] = ids.size
      result
    }
  end