input: Write a function to convert degrees Fahrenheit to degrees Celsius. The function should take a single input, the temperature in Fahrenheit, and return the temperature in Celsius.
  assert FahrenheitToCelsius(32) == 0
  assert FahrenheitToCelsius(212) == 100
  assert FahrenheitToCelsius(-40) == -40
  assert FahrenheitToCelsius(98.6) == 37
  assert FahrenheitToCelsius(0) == -17.77777777777778
output: def FahrenheitToCelsius(fahrenheit):
      return (fahrenheit - 32) * 5 / 9