input: Write a python function to generate the first n numbers in the Fibonacci series.
  assert generate_fibonacci(10) == [0, 1, 1, 2, 3, 5, 8, 13, 21, 34]
  assert generate_fibonacci(5) == [0, 1, 1, 2, 3]
  assert generate_fibonacci(1) == [0]
output: def generate_fibonacci(n):
      if n <= 0:
          return []
      elif n == 1:
          return [0]
      
      fib_series = [0, 1]
      while len(fib_series) < n:
          fib_series.append(fib_series[-1] + fib_series[-2])
      return fib_series