def fetch_master_by_level
      masters = Keynote.fetch_master_slide_names

      {}.tap do |result|
        masters.each do |master|
          if master.match(/\Ah(?<level>[1-5])\z/)
            level = Integer(Regexp.last_match[:level])
            result[level] = master
          elsif master == 'cover'
            result[COVER_LEVEL] = 'cover'
          end
        end
      end
    end
def fetch_master_by_level
      masters = Keynote.fetch_master_slide_names

      {}.tap do |result|
        masters.each do |master|
          if master.match(/\Ah(?<level>[1-5])\z/)
            level = Integer(Regexp.last_match[:level])
            result[level] = master
          elsif master == 'cover'
            result[COVER_LEVEL] = 'cover'
          end
        end
      end
    end
Find master names like "h1", "h2", ... and return { 1 => "h1", 2 => "h2" } only for available ones.
 @return [Hash{ Integer => String }]