input: Write a function to remove all 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("A")=="A"
  assert remove_duplicates("AAAA")=="A"
  assert remove_duplicates("")==""
  assert remove_duplicates("ABBCCBAAA")=="ABCBA"
output: def remove_duplicates(string): 
      result = "" 
      prev = '' 
  
      for char in string:
          if char != prev: 
              result += char
              prev = char
      return result