input: Write a python function to get the current temperature of a given city using openweathermap API.
  assert get_weather_temperature('London') == 280.32
  assert get_weather_temperature('New York') == 289.65
  assert get_weather_temperature('Tokyo') == 295.15
output: import requests
  
  def get_weather_temperature(city):
      api_key = "your_api_key"  # Replace with your OpenWeatherMap API key
      base_url = "http://api.openweathermap.org/data/2.5/weather?"
      
      complete_url = base_url + "q=" + city + "&appid=" + api_key
      response = requests.get(complete_url)
      data = response.json()
      
      if data["cod"] != "404":
          main = data["main"]
          temperature = main["temp"]
          return temperature
      else:
          return None