code: def change_charset(s, original_charset, target_charset):
      
      if not isinstance(s, str):
          raise ValueError('"s" must be a string.')
  
      intermediate_integer = charset_to_int(s, original_charset)
      output_string = int_to_charset(intermediate_integer, target_charset)
      return output_string
docs: Convert a string from one charset to another.