input: Write a python function to determine the performance complexity of a given code snippet.
  assert determine_complexity("The performance complexity of the code snippet is O(n).") == "O(n)"
  assert determine_complexity("The performance complexity of the code snippet is O(1).") == "O(1)"
  assert determine_complexity("The performance complexity of the code snippet is O(n^2).") == "O(n^2)"
output: def determine_complexity(code_snippet: str) -> str:
      import re
      match = re.search(r'O\([^)]+\)', code_snippet)
      return match.group(0) if match else ""