input: Write a python function to generate a specified number of random news headlines from a given list of headlines.
  assert len(generate_random_headlines(["Headline 1", "Headline 2", "Headline 3"], 2)) == 2
  assert len(generate_random_headlines(["Headline 1", "Headline 2", "Headline 3", "Headline 4"], 3)) == 3
  assert set(generate_random_headlines(["Headline 1"], 1)) == {"Headline 1"}
output: import random
  
  def generate_random_headlines(headlines, num):
      return random.sample(headlines, num)