input: Write a function to find the largest three numbers in a list. The function should return a list containing the three largest numbers in descending order. If the list has fewer than three numbers, the function should return all the numbers in the list in descending order.
  
  assert find_largest_three_numbers([1, 6, 3, 8, 7, 4])==[8, 7, 6]
  assert find_largest_three_numbers([5, 2, 9, 1, 7])==[9, 7, 5]
  assert find_largest_three_numbers([10, 3, 20])==[20, 10, 3]
  assert find_largest_three_numbers([1, 2])==[2, 1]
  assert find_largest_three_numbers([])==[]
output: def find_largest_three_numbers(nums):
      return sorted(nums, reverse=True)[:3]