input: Write a function to print the Fibonacci series up to n numbers where n is a user input. If n is less than or equal to 0, the function should print an empty string.
  assert print_fibonacci(10)=="0 1 1 2 3 5 8 13 21 34 "
  assert print_fibonacci(1)=="0 "
  assert print_fibonacci(0)==""
  assert print_fibonacci(5)=="0 1 1 2 3 "
output: def print_fibonacci(n):
      if n <= 0:
          return ""
      fib_series = []
      a, b = 0, 1
      for _ in range(n):
          fib_series.append(str(a))
          a, b = b, a + b
      return " ".join(fib_series) + " "