input: Write a python function to manage a set of strings by adding, checking, and removing elements.
  assert manage_string_set(["add", "Python", "add", "Java", "add", "C#", "add", "JavaScript", "check", "Python", "remove", "Java", "print"]) == {"Python", "C#", "JavaScript"}
  assert manage_string_set(["add", "Go", "add", "Ruby", "check", "Go", "remove", "Ruby", "print"]) == {"Go"}
  assert manage_string_set(["add", "Swift", "add", "Kotlin", "add", "Perl", "check", "Swift", "remove", "Kotlin", "print"]) == {"Swift", "Perl"}
output: def manage_string_set(commands):
      s = set()
      i = 0
      while i < len(commands):
          command = commands[i]
          if command == "add":
              s.add(commands[i+1])
              i += 2
          elif command == "check":
              i += 2
          elif command == "remove":
              s.remove(commands[i+1])
              i += 2
          elif command == "print":
              return s
      return s