def engine_options(additional_options = {})
      opts = options.merge(additional_options)
      opts[:load_paths] = load_paths(opts)
      options[:sourcemap] = :auto if options[:sourcemap] == true
      options[:sourcemap] = :none if options[:sourcemap] == false
      opts
    end
def engine_options(additional_options = {})
      opts = options.merge(additional_options)
      opts[:load_paths] = load_paths(opts)
      options[:sourcemap] = :auto if options[:sourcemap] == true
      options[:sourcemap] = :none if options[:sourcemap] == false
      opts
    end
Non-destructively modifies \{#options} so that default values are properly set,
 and returns the result.

 @param additional_options [{Symbol => Object}] An options hash with which to merge \{#options}
 @return [{Symbol => Object}] The modified options hash