input: Write a function to return true if the first string contains the second string. If the first string does not contain the second string, return false. If either of the strings is empty, return False.
  assert check_contains("catering", "cat")==True
  assert check_contains("apple", "orange")==False
  assert check_contains("banana", "ana")==True
  assert check_contains("", "cat")==False
  assert check_contains("cat", "")==False
output: def check_contains(s1, s2):
      if not s1 or not s2:
          return False
      return s2 in s1