input: def Fibonacci(n):
      """Generate a Fibonacci sequence of first n numbers.
      Example:
      for Fibonacci(10)
      0
      1
      1
      2
      3
      5
      8
      13
      21
      """
output:     if n <= 0:
          return []
      elif n == 1:
          return [0]
      elif n == 2:
          return [0, 1]
      
      fib_sequence = [0, 1]
      for i in range(2, n):
          fib_sequence.append(fib_sequence[-1] + fib_sequence[-2])
      
      return fib_sequence