input: Write a python function to detect duplicate characters in a string.
  assert detect_duplicate_characters("hello") == True
  assert detect_duplicate_characters("world") == False
  assert detect_duplicate_characters("python") == False
  assert detect_duplicate_characters("programming") == True
output: def detect_duplicate_characters(s):
      seen = set()
      for char in s:
          if char in seen:
              return True
          seen.add(char)
      return False