input: Write a Python function to simulate the GPIO setup and handling for different operating modes, including checking user licenses and potentially opening a solenoid valve. 
  assert simulated_gpio_handling("normal", "valid_license_text") == "Beer time!"
  assert simulated_gpio_handling("party", "valid_license_text") == "Beer time!"
  assert simulated_gpio_handling("barkeep", "valid_license_text", BAC=0.05, intoxicated=0.08) == "Beer time!"
  assert simulated_gpio_handling("barkeep", "valid_license_text", BAC=0.09, intoxicated=0.08) == "You are too drunk, beer time is over"
output: def simulated_gpio_handling(mode, license_text, BAC=None, intoxicated=None):
      def check_license(license_text):
          # Simulated license check
          return license_text == "valid_license_text"
  
      if not check_license(license_text):
          return "Invalid license"
  
      if mode in ["normal", "party"]:
          return "Beer time!"
  
      if mode == "barkeep":
          if BAC is not None and intoxicated is not None:
              if BAC > intoxicated:
                  return "You are too drunk, beer time is over"
              return "Beer time!"
          return "BAC or intoxicated level not provided"
  
      return "Unknown mode"