def identify_class(obj)
    # write your case control structure here
    case obj
        when Hacker
        puts  "It's a Hacker!"
        
        when Submission
        puts "It's a Submission!"
        
        when TestCase
        puts "It's a TestCase!"
        
        when Contest
        puts "It's a Contest!"
        
        else
        puts "It's an unknown model"
        
    end
end