input: Write a function to convert degrees Fahrenheit to degrees Celsius. The function should take a single argument, `temp_fahrenheit`, which is the temperature in degrees Fahrenheit, and return the equivalent temperature in degrees Celsius. If the input temperature is empty, the function should return 0.
  
  def FahrenheitToCelsius(temp_fahrenheit):
      if temp_fahrenheit is None:
          return 0
      temp_celsius = (temp_fahrenheit - 32) * 5/9
      return temp_celsius
  
  assert FahrenheitToCelsius(32)==0
  assert FahrenheitToCelsius(212)==100
  assert FahrenheitToCelsius(-40)==-40
  assert FahrenheitToCelsius(None)==0
output: def FahrenheitToCelsius(temp_fahrenheit):
      if temp_fahrenheit is None:
          return 0
      temp_celsius = (temp_fahrenheit - 32) * 5/9
      return temp_celsius