input: Write a python function to convert Fahrenheit to Celsius.
  assert TempConverter(32).convert_f_to_c() == 0
  assert TempConverter(212).convert_f_to_c() == 100
  assert TempConverter(98.6).convert_f_to_c() == 37
output: class TempConverter:
      def __init__(self, fahrenheit):
          self.fahrenheit = fahrenheit
  
      def convert_f_to_c(self):
          return (self.fahrenheit - 32) * 5 / 9