This might be a dumb question but I recently stumbled upon this code in Django Rest Framework, couldn't find out what is the _() inside that dictionary...
class SlugField(CharField):
default_error_messages = {
'invalid': _('Enter a valid "slug" consisting of letters, numbers, underscores or hyphens.'),
'invalid_unicode': _('Enter a valid "slug" consisting of Unicode letters, numbers, underscores, or hyphens.')
}