def clean(self, py_value):
        """
        Cleans the value before storing it.

        :param:     py_value : <str>

        :return:    <str>
        """
        try:
            from webhelpers.text import strip_tags
            return strip_tags(py_value)
        except ImportError:
            warnings.warn('Unable to clean string column without webhelpers installed.')
            return py_value