input: def Fibonacci(n):
      """Generate a Fibonacci sequence of first n numbers.
      >>> Fibonacci(10)
      [0, 1, 1, 2, 3, 5, 8, 13, 21, 34]
      """
      if n==1:
          return [0]
      elif n==2:
          return [0, 1]
      else:
          fib_sequence = [0, 1]
          for i in range(2, n):
              fib_sequence.append(fib_sequence[-1] + fib_sequence[-2])
          return fib_sequence
output:     if n==1:
          return [0]
      elif n==2:
          return [0, 1]
      else:
          fib_sequence = [0, 1]
          for i in range(2, n):
              fib_sequence.append(fib_sequence[-1] + fib_sequence[-2])
          return fib_sequence