code: def replace(cls, replacement_string):
          
          e = cls()
  
          def _replace_emoji(match):
              val = match.group(1)
              if val in e:
                  return e._image_string(match.group(1))
              else:
                  return match.group(0)
  
          return e._pattern.sub(_replace_emoji, replacement_string)
docs: Add in valid emojis in a string where a valid emoji is between ::