def enrich(self, column):
        """ This enricher returns the same dataframe
        with a new column named 'domain'.
        That column is the result of splitting the
        email address of another column. If there is
        not a proper email address an 'unknown'
        domain is returned.

        :param column: column where the text to analyze is found
        :type data: string
        """

        if column not in self.data.columns:
            return self.data

        self.data['domain'] = self.data[column].apply(lambda x: self.__parse_email(x))
        return self.data