input: Write a python function to find the largest of three numbers.
  assert max_number(3, 6, 9) == "The largest number is 9"
  assert max_number(10, 5, 8) == "The largest number is 10"
  assert max_number(1, 2, 3) == "The largest number is 3"
output: def max_number(a, b, c):
      largest = max(a, b, c)
      return f"The largest number is {largest}"