input: Write a function to generate Fibonacci series up to a given number of terms.
  assert generate_fibonacci(5) == [1, 1, 2, 3, 5]
  assert generate_fibonacci(10) == [1, 1, 2, 3, 5, 8, 13, 21, 34, 55]
  assert generate_fibonacci(3) == [1, 1, 2]
output: def generate_fibonacci(n):
      if n <= 0:
          return []
      elif n == 1:
          return [1]
      fib_series = [1, 1]
      while len(fib_series) < n:
          fib_series.append(fib_series[-1] + fib_series[-2])
      return fib_series