input: Write a function to print the Fibonacci series up to a given number. The function should take an integer `n` as input and print all Fibonacci numbers that are less than or equal to `n`.
  assert fibonacci(5) == [0, 1, 1, 2, 3, 5]
  assert fibonacci(0) == [0]
  assert fibonacci(-1) == []
  assert fibonacci(13) == [0, 1, 1, 2, 3, 5, 8, 13]
  assert fibonacci(1) == [0, 1, 1]
output: def fibonacci(n):
      if n < 0:
          return []
      result = []
      a, b = 0, 1
      while a <= n:
          result.append(a)
          a, b = b, a + b
      return result