input: Write a python function to simulate a coin toss and return the result as 'Heads' or 'Tails'.
  assert coin_toss() in ['Heads', 'Tails']
  assert isinstance(coin_toss(), str)
output: import random
  
  def coin_toss():
      return 'Heads' if random.randint(0, 1) == 0 else 'Tails'