input: Write a python function to generate a list of Fibonacci numbers of a given length.
  assert fibonacci(5) == [1, 1, 2, 3, 5]
  assert fibonacci(7) == [1, 1, 2, 3, 5, 8, 13]
  assert fibonacci(10) == [1, 1, 2, 3, 5, 8, 13, 21, 34, 55]
output: def fibonacci(n):
      if n <= 0:
          return []
      elif n == 1:
          return [1]
      fibonacci_sequence = [1, 1]
      while len(fibonacci_sequence) < n:
          fibonacci_sequence.append(fibonacci_sequence[-1] + fibonacci_sequence[-2])
      return fibonacci_sequence