Returns code for given key (one cell)

        Parameters
        ----------

        key: 3-Tuple of Integer
        \t Cell key

def _get_code(self, key):
        """Returns code for given key (one cell)

        Parameters
        ----------

        key: 3-Tuple of Integer
        \t Cell key

        """

        data = self.grid.code_array(key)
        self.grid.code_array.result_cache.clear()

        return data