Initialize form metadata

def _init_metadata(self, **kwargs):
        """Initialize form metadata"""
        osid_objects.OsidObjectForm._init_metadata(self, **kwargs)
        self._numeric_score_increment_default = self._mdata['numeric_score_increment']['default_decimal_values'][0]
        self._lowest_numeric_score_default = self._mdata['lowest_numeric_score']['default_decimal_values'][0]
        self._based_on_grades_default = self._mdata['based_on_grades']['default_boolean_values'][0]
        self._highest_numeric_score_default = self._mdata['highest_numeric_score']['default_decimal_values'][0]