input: Write a function to check if a given string contains the word "Hello". If the word "Hello" is found within the string, return True; otherwise, return False. If the string is empty, return False.
  assert check_hello("Hello, World!")==True
  assert check_hello("Hi there, how are you?")==False
  assert check_hello("")==False
output: def check_hello(s):
      if not s:
          return False
      return "Hello" in s