input: Write a function to generate and print the Fibonacci series up to n numbers where n is a user input. The function should take an integer input n and print the Fibonacci sequence up to the nth number.
  assert fibonacci_series(10)=="Fibonacci Series:\n0 1 1 2 3 5 8 13 21 34 "
  assert fibonacci_series(5)=="Fibonacci Series:\n0 1 1 2 3 "
  assert fibonacci_series(0)=="Fibonacci Series:\n"
  assert fibonacci_series(-5)=="Fibonacci Series:\n"
  assert fibonacci_series(1)=="Fibonacci Series:\n0 "
output: def fibonacci_series(n):
      if n <= 0:
          return "Fibonacci Series:\n"
      result = "Fibonacci Series:\n0 "
      a, b = 0, 1
      for _ in range(1, n):
          result += f"{b} "
          a, b = b, a + b
      return result