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, return an empty list.
  def fibonacci_series(n):
      if n <= 0:
          return []
      a, b = 0, 1
      series = [a, b]
      for i in range(2, n):
          c = a + b
          a, b = b, c
          series.append(c)
      return series
  
  assert fibonacci_series(10) == [0, 1, 1, 2, 3, 5, 8, 13, 21, 34]
  assert fibonacci_series(1) == [0]
  assert fibonacci_series(0) == []
  assert fibonacci_series(2) == [0, 1]
  assert fibonacci_series(5) == [0, 1, 1, 2, 3]
output: def fibonacci_series(n):
      if n <= 0:
          return []
      a, b = 0, 1
      series = [a]
      for i in range(1, n):
          series.append(b)
          a, b = b, a + b
      return series