input: Write a function to design a web server in Python using the Flask framework that would serve a JSON object containing the current temperature for a city based on the city name given in the request. The function should return the temperature in the main dictionary of the JSON response from the OpenWeatherMap API.
  assert get_temp('London')=={'temperature': 280.15}
  assert get_temp('New York')=={'temperature': 285.15}
  assert get_temp('Tokyo')=={'temperature': 290.15}
  assert get_temp('Paris')=={'temperature': 282.15}
  assert get_temp('Berlin')=={'temperature': 281.15}
output: def get_temp(city):
      import requests
      api_key = 'your_openweathermap_api_key'
      url = f'http://api.openweathermap.org/data/2.5/weather?q={city}&appid={api_key}'
      response = requests.get(url)
      data = response.json()
      return {'temperature': data['main']['temp']}