nl: the %(lookup)s in %(date_field)s.", where '%(field_name)s' is replaced with third element of data_check, '%(date_field)s' is replaced with fourth element of date_check and '%(lookup)s' is replaced with result of the function, six.text_type called with second element of date_check as an argument, return the result. define the method get_form_error with an argument self.
code: def get_form_error ( self ) :