input: Write a function to return True if the given string contains the word "Hello", otherwise return False. The function should be named `check_hello`.
  
  assert check_hello("Hello World")==True
  assert check_hello("Hi there!")==False
  assert check_hello("Say Hello to my little friend")==True
  assert check_hello("")==False
  assert check_hello("This is a test string")==False
output: def check_hello(s):
      return "Hello" in s