input: Write a python function to generate a list of Fibonacci numbers less than a given number.
  assert fibonacci(10) == [0, 1, 1, 2, 3, 5, 8]
  assert fibonacci(15) == [0, 1, 1, 2, 3, 5, 8, 13]
  assert fibonacci(1) == [0]
output: def fibonacci(n):
      if n <= 0:
          return []
      fib_list = [0, 1]
      while True:
          next_fib = fib_list[-1] + fib_list[-2]
          if next_fib >= n:
              break
          fib_list.append(next_fib)
      return fib_list if n > 1 else [0]