input: Write a function to check if a given string contains the word "Hello". If it does, return True, otherwise return False.
  assert check_hello("Hello, how are you?")==True
  assert check_hello("Hi there!")==False
  assert check_hello("Testing Hello World")==True
  assert check_hello("Just another string")==False
  assert check_hello("")==False
output: def check_hello(s):
      return "Hello" in s