input: Write a python function to remove consecutive duplicate characters from a string.
  assert remove_duplicates("AAABBCCCD") == "ABCD"
  assert remove_duplicates("AABBCC") == "ABC"
  assert remove_duplicates("ABABAB") == "ABABAB"
  assert remove_duplicates("A") == "A"
  assert remove_duplicates("") == ""
output: def remove_duplicates(s):
      if not s:
          return ""
      
      result = [s[0]]
      
      for char in s[1:]:
          if char != result[-1]:
              result.append(char)
      
      return ''.join(result)