I got stuck in duling grounds

2

@zisu0426 please use the formatted text button to format the code so we can see the tabs and indents

loop:
# Find and attack the enemy inside a loop.
# When you're done, submit to the multiplayer ladder!
enemy = hero.findNearestEnemy()
hero.attack(enemy)

is different from

loop:
    # Find and attack the enemy inside a loop.
    # When you're done, submit to the multiplayer ladder!
    enemy = hero.findNearestEnemy()
    hero.attack(enemy)

Also see this guide if you would to know more about multiplayer.