def _parseField(self, value, filename=None):
        if value is None:
            value = ''
        elif self._vocabulary is not None:
            value = title_or_value(self._vocabulary, value)

        return AsTextDiff._parseField(self, value, filename)
    def _parseField(self, value, filename=None):
        if value is None:
            value = ''
        elif self._vocabulary is not None:
            value = title_or_value(self._vocabulary, value)

        return AsTextDiff._parseField(self, value, filename)
    def _parseField(self, value, filename=None):
        value = unicode('' if (value is None) else value)

        # In tests translation is not available, so we account for this
        # case here.
        translate = getattr(getSite(), 'translate', None)
        if translate is not None:
            value = translate(_(value))

        return AsTextDiff._parseField(self, value, filename)