input: Write a function to check if a given string contains the word "Hello". If the string contains "Hello", return True; otherwise, return False.
  assert check_hello("Hello World")==True
  assert check_hello("Hi there")==False
  assert check_hello("Say Hello")==True
  assert check_hello("hello")==False
  assert check_hello("")==False
output: def check_hello(s):
      return "Hello" in s