def transform(self, word, column=Profile.GRAPHEME_COL, error=errors.replace):
        """
        Transform a string's graphemes into the mappings given in a different column
        in the orthography profile.

        Parameters
        ----------
        word : str
            The input string to be tokenized.

        column : str (default = "Grapheme")
            The label of the column to transform to. Default it to tokenize with
            orthography profile.

        Returns
        -------
        result : list of lists
            Result of the transformation.

        """
        assert self.op, 'method can only be called with orthography profile.'

        if column != Profile.GRAPHEME_COL and column not in self.op.column_labels:
            raise ValueError("Column {0} not found in profile.".format(column))

        word = self.op.tree.parse(word, error)
        if column == Profile.GRAPHEME_COL:
            return word
        out = []
        for token in word:
            try:
                target = self.op.graphemes[token][column]
            except KeyError:
                target = self._errors['replace'](token)
            if target is not None:
                if isinstance(target, (tuple, list)):
                    out.extend(target)
                else:
                    out.append(target)
        return out