code: def cipher_block (self, state):
          
          # PKCS7 Padding
          state=state+[16-len(state)]*(16-len(state))# Fails test if it changes the input with +=
  
          self._add_round_key(state, 0)
  
          for i in range(1, self._Nr):
              self._sub_bytes(state)
              self._shift_rows(state)
              self._mix_columns(state, False)
              self._add_round_key(state, i)
  
          self._sub_bytes(state)
          self._shift_rows(state)
          self._add_round_key(state, self._Nr)
          return state
docs: Perform AES block cipher on input