input: Write a python function to fetch weather data using the OpenWeatherMap API and return the temperature and humidity of a given city.
  assert fetch_weather_data('New York') == (temperature_value, humidity_value)
  assert fetch_weather_data('Los Angeles') == (temperature_value, humidity_value)
  assert fetch_weather_data('Chicago') == (temperature_value, humidity_value)
output: def fetch_weather_data(city):
      import requests
  
      api_key = 'your_api_key_here'  # Replace with your OpenWeatherMap API key
      base_url = 'http://api.openweathermap.org/data/2.5/weather'
  
      params = {
          'q': city,
          'appid': api_key,
          'units': 'metric'  # Use 'imperial' for Fahrenheit
      }
  
      response = requests.get(base_url, params=params)
      data = response.json()
  
      if response.status_code == 200:
          temperature = data['main']['temp']
          humidity = data['main']['humidity']
          return temperature, humidity
      else:
          raise Exception(f"Error fetching data for {city}: {data.get('message', 'No additional information')}")