input: Write a function to remove all the consecutive duplicates from a given string. If the given string is empty, return an empty string.
  def remove_duplicates(string):
      result = ""
      prev = ''
  
      for char in string:
          if char != prev:
              result += char
              prev = char
      return result
  
  assert remove_duplicates("AAABBCCCD")=="ABCD"
  assert remove_duplicates("aabccba")=="abcba"
  assert remove_duplicates("abcde")=="abcde"
  assert remove_duplicates("")==""
  assert remove_duplicates("a")=="a"
output: def remove_duplicates(string):
      result = ""
      prev = ''
  
      for char in string:
          if char != prev:
              result += char
              prev = char
      return result