input: Write a python function to convert a floating point number to a string with two decimal places.
  assert float_to_string(123.456) == "123.46"
  assert float_to_string(10.1) == "10.10"
  assert float_to_string(3.9999) == "4.00"
output: def float_to_string(number):
      return f"{number:.2f}"