input: Write a function to determine 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 to John")==True
  assert check_hello("hello world")==False
  assert check_hello("")==False
output: def check_hello(s):
      return "Hello" in s