input: Write a function that prints the Fibonacci series up to n numbers where n is provided as input. The function should first print the first two numbers, 0 and 1, and then follow up with the rest of the series. Include assertions to verify the correctness of the function.
  
  assert fibonacci(10) == "0 1 1 2 3 5 8 13 21 34"
  assert fibonacci(0) == ""
  assert fibonacci(1) == "0"
  assert fibonacci(2) == "0 1"
  assert fibonacci(5) == "0 1 1 2 3"
  assert fibonacci(8) == "0 1 1 2 3 5 8 13"
output: def fibonacci(n):
      if n == 0:
          return ""
      if n == 1:
          return "0"
      result = "0 1"
      a, b = 0, 1
      for _ in range(2, n):
          a, b = b, a + b
          result += f" {b}"
      return result